Window fitter invoice template UK (2026): FENSA, CIS and VAT

A window fitter's invoice has to do two jobs at once. It has to reconcile money against a survey that was taken weeks earlier, and it has to point the customer at the compliance paperwork that turns six new frames into a legal installation. "Supply and fit windows as quoted" achieves neither. It does not tell a householder which apertures were surveyed, which unit was remade after the brickwork came back 40 mm out, whether the trickle vents were part of the price, or when their FENSA certificate will arrive. It does not tell a main contractor's quantity surveyor which plot, which elevation and which valuation period to price. And it does not tell a Construction Industry Scheme contractor how much of the payment is labour and how much is the direct cost of the units you bought.

Replacement window and door installation is a different invoicing problem from emergency glazing. The sibling guide, glazier invoice template UK, covers the board-up, the failed sealed unit and the same-day re-glaze, where the money is small, the tax point is immediate and there is no manufacturing lead time. This page covers the other half of the trade: a surveyed order, made-to-measure frames, a deposit taken before anything is cut, a fitting week, and a self-certified Building Regulations record at the end of it.

Three things drive the invoice. The payer decides whether the Construction Industry Scheme applies at all. The building and the contract decide the VAT rate. The product decides whether you can take a deposit and keep it, because bespoke frames are not stock goods a customer can hand back.

This guide gives copy-paste fields, a labour and materials split, line-item wording, deposit and stage logic, variations for non-standard apertures, six worked examples and a practical treatment of CIS, VAT, the domestic reverse charge, FENSA and Certass self-certification and the Building Regulations parts a window job actually touches. Every money figure is illustrative only. It is arithmetic to show invoice layout, not a price list and not a claim about UK market rates.

Rules and links were checked for this guide on 3 September 2026. This is general information, not tax, legal or Building Regulations advice. InvoiceAdept is invoicing software from Tech Me Today Ltd, Companies House 15917255, ICO ZB944663. InvoiceAdept does not file VAT returns, CIS300 returns, Making Tax Digital updates or Self Assessment, and it does not issue FENSA, Certass or Building Control certificates.

In short

Work out who pays you, what the building is, and whether the frames were made to the customer's sizes. Everything else follows.

• Private householder, replacement windows in their existing home: no CIS. If you are VAT-registered, this is normally 20%. Take a deposit if your accepted terms say so, invoice it, and tell the customer when their FENSA or Certass certificate will be lodged.

• Main contractor, developer or a bigger glazing firm pays you: supply-and-fix installation is within CIS. Split labour from materials at your direct cost. If both businesses are VAT and CIS registered, the supply is standard or reduced rated and the customer has not notified you as an end user, the domestic reverse charge applies and you do not add VAT to the payment.

• Supply and deliver frames only, no installation: manufacture and delivery of glazing materials and doors sits outside CIS. Write "supply and deliver only, no installation" on the face of the invoice.

On the VAT side, a straight replacement in a lived-in house is standard-rated. The reliefs are real but narrow: 0% only in the course of constructing a qualifying new dwelling, and 5% only on a qualifying conversion or a property that has genuinely not been lived in for two years. Double glazing installed during one of those qualifying jobs can take the 5% rate as improvement work to the fabric, which is a rule most window fitters have never read.

On the deposit side, made-to-measure frames are goods made to the consumer's specifications. That removes the normal 14-day off-premises cancellation right, but only if you have set the contract up properly and told the customer. Get that wording on the order and repeat it on the deposit invoice.

Start with the invoice generator if you want a numbered document today. InvoiceAdept Free is £0 for five invoices a month, Pro is £7.99 excl VAT and Pro+ is £12.99 excl VAT with CIS features. A single six-window job can easily use three or four documents once you count the deposit, the balance and a variation, so count your documents before you choose a plan.

Three window jobs, three invoices

These three jobs can use identical frames from the same fabricator and still need different invoices.

The trap in the middle column is that the finished window belongs to a homeowner while the payment comes from a business. HMRC's CISR14020 makes clear that the contract to test is the one between the contractor and you, not the ownership of the building. If a builder doing a loft conversion pays you to fit four new windows, that payment can be within CIS even though a family lives there. If the family hires you directly, it is not.

What window and door work belongs on the invoice

Do not compress a surveyed, manufactured, fitted and certified job into one line. Describe the apertures, the product, the labour and the compliance work separately, and say plainly what somebody else supplied.

If a builder, plasterer or decorator is doing the making good and billing the customer separately, write "by others, not charged on this invoice". If you engaged and paid a subcontract fitting team as part of your package, the customer sees your package lines and you keep the subcontractor's invoice and CIS deduction statement in your own records.

What a UK window fitter invoice must include

The starting point is the GOV.UK list of invoice particulars:

• a unique identification number

• your business name, address and contact information

• the name and address of the customer you are invoicing

• a clear description of what you are charging for

• the date the goods or service were provided, and the date of the invoice

• the amounts being charged, the VAT amount if applicable, and the total owed

GOV.UK adds two structural points that catch out window firms in particular. A sole trader must also show their own name alongside any trading name, plus an address where legal documents can be delivered if a business name is used. A limited company must show the full company name exactly as it appears on the certificate of incorporation, and if you decide to name any directors you must name all of them.

If you are VAT-registered, a full VAT invoice needs more. HMRC's VATREC5010 sets out the particulars required by regulation 14(1) of the VAT Regulations 1995.

Keep your business records for VAT purposes for at least six years (Notice 700/21). For a window fitter that means the survey sheet, the fabricator's order confirmation, the deposit invoice, the delivery note, the certificate reference and the signed completion note, not just the final invoice.

Put the installation address on the invoice even where it matches the billing address, because the certificate and any future conveyancing search will be tied to the property, not to the payer. For contractor work, add plot, block, elevation, purchase order, application number and the week-ending date. One clear header line stops a quantity surveyor phoning the contracts manager to ask which windows you mean.

Copy-paste window fitter invoice fields

Delete anything that does not apply. Never leave a CIS or reverse-charge placeholder on a private householder's bill.

INVOICE NUMBER / INVOICE DATE / SUPPLY OR TAX-POINT DATE / DUE DATE

SUPPLIER
Legal name:
Trading name (if any):
Address, service address for legal documents, phone, email:
Company number + registered office (limited company only):
VAT number (only if VAT-registered):
Self-certification scheme and registration number (FENSA / Certass / other):
UTR (only where a CIS contractor needs it):

CUSTOMER AND JOB
Customer legal name and billing address:
Installation address / plot / block / elevation:
Survey reference and survey date:
Quote / order / purchase-order reference:
Aperture schedule reference (W1, W2, D1 and so on):
Stage: survey / deposit / manufacture / fit / balance / snag / retention / variation:
Dates worked, or supply date:

LINES
Survey and check measure:
Strip-out and disposal of existing frames and glass:
Frames, doorsets and sealed units supplied — quantity, system, colour, glazing spec:
Hardware — handles, hinges, restrictors, locks, cylinders:
Trickle vents / background ventilators — rooms and equivalent area:
Cills, trims, add-ons, cloaking fillets:
Installation labour — apertures fitted, dates:
Making good — plaster, render, mastic, decoration if in scope:
Access — scaffold or tower hire shown separately from erect/dismantle labour:
Waste — skip or tip charges:
Certification / Building Control application fee:
Materials at your direct cost — invoices on file:
Free-issue or client-supplied items — note only, not your materials charge:
Variation reference and written approval:

TOTALS
Labour subtotal:
Materials direct-cost subtotal:
Other agreed charges (access, waste, certification):
Net subtotal:
VAT rate and amount, OR reverse-charge wording if applicable:
CIS deduction rate and the base it is applied to (contractor invoice only):
Deposit and stage payments already received, with their invoice numbers:
Retention withheld and the release trigger (if agreed):
BALANCE DUE:
Payment method / bank details / payment link:

ATTACHMENTS, NOT THE INVOICE
Aperture schedule and survey sheet
Product data sheet, U-value or Window Energy Rating evidence
FENSA / Certass certificate or Building Control completion record
Insurance-backed guarantee documentation
Signed completion and snag note

Deposit invoices, balance invoices and variation invoices should all sit in the same number series. Two series, or a deposit taken on a scrap of paper, is how a window firm ends up unable to prove what the customer already paid.

Labour versus materials for window installation

The split matters for three separate reasons, and window fitters routinely get it wrong because the frames are such a large share of the price.

First, CIS. A deduction is applied only to the part of the payment that does not represent the direct cost of materials to you. CISR15060 is explicit that "direct cost" means what you can demonstrate you actually paid, and that mark-up is not direct cost. It also warns against exactly the dodge that tempts a supply-and-fix window firm: claiming the whole charge is for the units and that installation is free. HMRC's guidance says the contractor must estimate the equipment cost if it is not specified, because in reality you incur a commercial cost for both the frames and their installation.

Second, free-issue frames. If a main contractor buys the windows and hands them to you to fit, they are not your materials and you cannot reduce your CIS base by their value. CISR15060 also covers the reimbursement case: if the contractor reimburses you for the frames, you are not entitled to a materials deduction for them either.

Third, the reverse charge. Where goods are supplied with construction services, HMRC's reverse charge technical guide treats that as a single supply for VAT purposes, and the reverse charge applies to the full value of the invoice. Splitting labour and materials into two contracts to dodge it does not work: if the contracts are linked and on the same site, the reverse charge applies to both.

Show the split on the face of a contractor invoice. "Labour £2,850. Materials at direct cost £6,410. CIS deduction applied to labour only." A quantity surveyor can approve that in thirty seconds. A single lump sum gets queried, and a queried invoice gets paid a month late.

CIS: when replacement window fitting is a construction operation

Start with the statute rather than trade folklore. Section 74(2)(a) of the Finance Act 2004, as summarised in CISR14100, brings the "construction, alteration, repair, extension, demolition or dismantling of buildings or structures (whether permanent or not)" within the scheme. CISR14020 puts it more bluntly: construction operations cover almost anything done to a building or structure, and the list expressly includes alteration and repair.

Taking out an existing window and fitting a new frame into the structural opening is work to the fabric of the building. It is not the manufacture of a component. HMRC's page on manufacture and delivery, CISR14220, draws the line for you in one sentence each way. Within CIS: "installation of manufactured items under 'supply and fix' arrangements". Excluded from CIS: "manufacture and delivery of flooring materials, glazing materials, computer and instrumentation systems, thermal insulation materials, heating and ventilation systems, doors and rolling grills, painting or decorating materials."

So the frames leaving the fabricator's yard are outside the scheme. The same frames going into a wall by your hands, for a contractor who pays you, are inside it.

That locksmith rule in CISR14210 is the one worth pinning to the office wall, because door work is where a window firm's CIS position becomes genuinely mixed. Swapping a euro cylinder is not a construction operation. Easing the frame, replacing the keep and making good the rebate is.

None of this touches a private householder. An ordinary homeowner is not a CIS contractor, so a domestic replacement job gets a normal numbered invoice with no deduction. A business that does not do construction work itself can still become a deemed contractor: GOV.UK's contractor guidance says registration is required where the business has spent more than £3 million on construction in the 12 months since its first payment. A property company, a hotel group or a landlord doing a large window programme can cross that line.

Those rates come straight from GOV.UK's make deductions and pay subcontractors page, which also confirms what comes out of the gross figure before the percentage is applied: VAT, consumable stores, fuel other than for travelling, plant hired for the job, and materials the subcontractor paid for directly. The contractor can ask for receipts, and will estimate if you cannot produce them. The same page requires the contractor to give you a payment and deduction statement within 14 days of the end of each tax month. Chase it. Those statements are how the deductions get credited against your tax bill.

VAT on replacement windows: standard-rated is the default

If you are VAT-registered, assume 20% and then look for a reason to depart from it. VAT Notice 708 opens paragraph 2.1 with the plain rule: "The construction of a new building and work to an existing building is normally standard-rated. There are various exceptions to this."

A straight replacement window job on a lived-in house is work to an existing building. There is no relief for making a house warmer, no relief because the old frames were rotten, and no relief because the customer is elderly or on benefits. The exceptions are about the building's status and the nature of the project, not the product.

You must register for VAT once your total taxable turnover for the last 12 months goes over £90,000, or when you expect it to exceed £90,000 in the next 30 days. GOV.UK's when to register page also sets the timing: you have 30 days from the end of the month in which you crossed the threshold, and your effective date of registration is the first day of the second month after that. A window firm that lands two large orders in one quarter can cross it faster than expected, so watch the rolling figure rather than the tax year. The longer walkthrough is in when to register for VAT UK.

Two lines in that table are worth expanding, because they contradict what installers often assume.

Scaffolding does not follow the job's rate. Notice 708 paragraphs 7.6 and 8.4 both list "the erection and dismantling of scaffolding" and "the hire of goods" among the services you must standard rate even where the rest of the contract qualifies for 5%. If you are running a reduced-rate empty-property job with a scaffold to the rear elevation, that scaffold line is 20% while the window installation is 5%. Split it on the invoice.

Listed buildings are not a relief. Notice 708 section 9 is now headed "Transitional historical arrangements" and states that all zero rating for approved alterations ended in September 2015, with the withdrawal itself effective from 1 October 2012. Paragraph 9.4.2 is still useful for a different reason: it puts "replacement of rotten wooden windows with uPVC double glazing" in the repair and maintenance column, and "replacement of uPVC double glazing with copies of original wooden windows for aesthetic reasons" in the alteration column. Even so, both are standard rated today. Heritage work is a conservation-officer problem, not a VAT saving.

One more piece of Notice 708 is worth knowing because customers ask about it. Paragraph 13.8.1 lists "window frames and glazing" among the articles that count as building materials for the purposes of the zero and reduced rates. That is why frames incorporated into a qualifying new dwelling can travel with the zero rate while, for example, carpets and fitted bedroom furniture cannot.

New builds, conversions, empty homes and listed dwellings

If a customer or a developer tells you the job is 0% or 5%, ask which section of Notice 708 they are relying on and who is holding the evidence. You are the one who has to answer for the rate on your return.

Section 8 has traps a window fitter will meet in practice. Paragraph 8.3.1 requires two clear years of the property not being lived in immediately before the work starts. Paragraph 8.3.3 lets you ignore occupation by squatters, occupation by "guardians", and non-residential use such as business storage. But paragraph 8.3.4's first rule is unforgiving: if the premises are already being lived in when your work starts, or have been lived in during the previous two years, all of your work is standard rated. Occasional use as a second home also kills it: paragraph 8.3.3 states that if the dwelling has been lived in on an occasional basis, for example because it was a second home, in the two years immediately before you start work, you cannot reduce rate your supply. And under 8.3.4's second rule, the reduced rate for a recently acquired single household dwelling only applies where your services are supplied to the occupier, which means a subcontract window fitter on that job must standard rate their work.

The practical takeaway: never apply 5% because a developer said so in a phone call. Get the basis in writing, keep the evidence, and if the position is genuinely unclear, charge 20% and let the customer take it up with their own adviser. Getting the rate wrong is your liability, not theirs.

Domestic reverse charge on glazing subcontract work

The domestic reverse charge is not a rate. It is a mechanism that moves the VAT accounting from you to your customer. GOV.UK's check when you must use the VAT domestic reverse charge page sets out that it applies to standard and reduced rate services, for businesses registered for VAT in the UK, reported within the Construction Industry Scheme. The list of services mirrors the CIS list, and it explicitly includes "constructing, altering, repairing, extending, demolishing or dismantling buildings or structures".

Run all five tests before you leave VAT off an invoice.

The end user rule is the one that catches window fitters, because it is optional and it must be in writing. HMRC's technical guide says an end user is a VAT and CIS registered business that does not make onward supplies of the construction services it receives, and that the reverse charge stops applying only once that customer tells you in writing. Until then, if the other conditions are met, you must apply the reverse charge even where you strongly suspect your customer is an end user. Notification can be by post, by email or written into the contract, and you keep it as part of your normal records.

The same guide answers three more questions that come up on glazing packages:

• Supply and fix is one supply. If goods are supplied with construction services, that is a single supply and the reverse charge applies to the full invoice value. HMRC even uses a fabrication example: a joiner who builds a staircase off site and installs it is making a reverse-charge service unless the installation element is 5% or less of the total charge. The same logic runs through a supply-and-fit window package.

• Splitting the contract does not help. If a customer enters into two linked contracts with you on the same site, one within CIS, the reverse charge applies to both. The guide states directly that charges for labour and the materials supplied in the course of that labour should not be separated to avoid applying the reverse charge to the materials.

• Scaffolding follows the project. For standard or reduced rated construction work, a contract for the hire, erection and dismantling of scaffolding is standard rated and goes through the reverse charge if the other conditions are met. Where the invoice shows one combined charge for hire plus labour, the full value is caught. On zero-rated new build housing, the reverse charge does not apply to the scaffolding. Hire of goods on its own is outside CIS entirely, so it never goes through the reverse charge.

Get the wording right. The technical guide requires you to show all the normal VAT invoice information, make it clear that the domestic reverse charge applies and that the customer must account for the VAT, and state how much VAT is due under the reverse charge, or the rate, without including it in the amount charged. It also lists acceptable phrasing:

• "VAT Act 1994 Section 55A applies"

• "S55A VATA 94 applies"

• "Customer to pay the VAT to HMRC"

And two absolute rules. Never reverse charge a private householder: the technical guide notes that where services are provided to a private domestic customer the reverse charge does not apply, because the customer is not VAT registered. Never reverse charge zero-rated new build work. The full walkthrough sits in domestic reverse charge VAT for construction.

FENSA, Certass and the certificate the customer expects

This is where a replacement window invoice differs from every other trade template. Replacing windows and doors is notifiable building work. GOV.UK's building regulations approval guidance lists "replace windows and doors" among the alteration projects that need approval, and then gives the alternative: "You do not need to get approval yourself if you use someone registered with a competent person scheme."

That is not marketing. Schedule 3 to the Building Regulations 2010 names the self-certification schemes. Paragraph 10 covers "installation, as a replacement, of a window, rooflight, roof window or door in an existing dwelling", and the persons who may self-certify are those registered for that type of work by Assure Certification Limited, Blue Flame Certification Limited, CERTASS Limited, Certsure LLP, Fensa Limited under the Fenestration Self-Assessment Scheme, or NAPIT Registration Limited. Paragraph 11 does the same job for existing buildings other than dwellings, and carves out glass which is load bearing or structural, glass forming part of glazed curtain walling, and revolving doors.

GOV.UK's use a competent person scheme page spells out the benefits: a registered installer can self-certify that their work complies, will tell the local authority on the customer's behalf if needed, and will give the customer a certificate within 8 weeks of completion which can be used as evidence of compliance and will show up in solicitors' searches. It adds that competent person schemes carry insurance-backed warranties and complaints procedures, and warns that the customer may have to correct the work or pay a fine if the regulations are not followed.

FENSA describes itself as a government-authorised scheme that monitors building regulation compliance for replacement windows and doors, and describes the certificate as "a declaration by the installation company to the homeowner" that the windows and doors comply with Building Regulations, use energy efficient products and are registered with the local council. It also verifies that the installer's warranty is insured. FENSA's own scope note is the part worth quoting on a quotation: it covers the replacement of external windows, doors, roof windows and rooflights in a home, but the property must be on its original footprint and the use and size of rooms must not be altered. It does not cover conservatories, porches, new builds, extensions, repairs where the frame is not included, or commercial properties.

Certass operates its own Competent Persons Scheme, under which approved members "can certify their installations to current Building Regulations as an alternative to using Building Control".

Two invoice rules follow. First, say which route applies, in writing, before the customer pays a deposit. Most disputes about window certificates start with a customer who assumed a certificate was coming on a job that was never eligible for one. Second, the invoice is not the certificate. It can name the scheme, the registration number and the lodgement date, and it can promise the document. It cannot substitute for it, and no invoicing software can issue one.

Parts L, F, K and B: what your paperwork can reference

A window fitter touches four parts of the Building Regulations on an ordinary replacement job. Naming them on the quotation and referencing them on the invoice is what separates a professional installer's paperwork from a scribbled total.

The current Approved Documents L and F both came into force on 15 June 2022, per the transitional arrangements published on the Approved Document L and Approved Document F pages. Those pages also note the transitional carve-out: the 2022 changes did not apply where a building notice or initial notice was given, or full plans deposited, before 15 June 2022, provided the work started before 15 June 2023. Both pages now also publish 2026 editions, and each of those documents states on its title page that it takes effect on 24 March 2027 for building work not connected with higher-risk building work, and 24 September 2027 for work that is. So the 2021 editions remain the operative guidance for a job you are pricing today.

Part L. Table 4.2 of Approved Document L, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments sets the limiting U-values for new fabric elements in existing dwellings.

Paragraph 4.8 adds a second limb that installers forget: a replacement element must be no worse than the element it replaces and meet Table 4.2. The timber transitional concessions in notes 9 and 13 have expired; the note states that from 15 June 2023 the full standard of 1.4 W/(m²·K), or Window Energy Rating band B, applies. Paragraph 10.3 requires that new and replacement windows, roof windows, rooflights and doors be draught-proofed, meet Table 4.2 and have insulated cavity closers installed where appropriate. Paragraph 10.4 confirms that a building control body may accept a Window Energy Rating or Doorset Energy Rating from a quality-assured certification scheme as evidence of compliance, which is exactly why the rating belongs on your invoice line. And paragraph 4.10 gives the heritage route: where the character of the building means Table 4.2 cannot be met, the fittings should not exceed a centre-pane U-value of 1.2 W/(m²·K), or single glazing should be supplemented with low-emissivity secondary glazing.

Part F. Approved Document F, Volume 1: Dwellings deals with replacement windows at paragraphs 3.14 to 3.16. If the existing windows had background ventilators, the replacements should include them, they should be no smaller than the originals, and they should be controllable automatically or by the occupant. If the size of the originals is unknown, the figures in paragraph 3.15 may be applied. Where the existing windows had no ventilators, paragraph 3.15 notes that replacing the windows is likely to increase airtightness, and that the ventilation provision must be no worse than before.

The document adds that where it is not technically feasible to hit those minimums, the ventilators should be as close to the minimum as is feasible. Paragraph 3.16 adds that where windows are replaced as part of a material change of use, Section 1 of the document applies as well.

Trickle vents are the single most common source of a window fitter's post-completion argument, because customers hear "draughts" and installers hear "compliance". Put them on the quotation as a line, put the room-by-room provision on the invoice, and the argument disappears.

Part K. Approved Document K is direct about scope at paragraph 0.2: glazing installed where there was none previously as part of the erection, extension or material alteration of a building, and the replacement of a whole unit, meaning the frame and glazing, is building work subject to requirements K4 and K5.2. Section 5 sets out the critical locations shown in Diagram 5.1: broadly, glazing in doors and door side panels up to 1,500 mm above floor level and within 300 mm of the door edge, and glazing in walls and partitions up to 800 mm above floor level. In those locations, paragraph 5.2 requires glazing that breaks safely, glazing that is robust or in small panes, or permanent protection. Paragraph 5.4 gives the standard: Class 3 of BS EN 12600 or Class C of BS 6206, or Class 2 or Class B where the pane is in a door or door side panel with a width exceeding 900 mm. Section 8 covers window controls, with paragraph 8.1 pointing at the reach dimensions in Diagram 8.1, and paragraph 8.2 requiring suitable opening limiters or guarding where a person might fall through a window above ground floor level.

Part B. Emergency escape windows are specified in Approved Document B, Volume 1: Dwellings at paragraph 2.10. The unobstructed openable area must be at least 0.33 m², with a minimum height of 450 mm and a minimum width of 450 mm, and the bottom of the openable area no more than 1,100 mm above the floor. The window must be capable of remaining open without being held. Locks with or without removable keys, and opening stays with child-resistant release catches, may be fitted. Paragraphs 2.1 and 2.2 identify where escape windows are needed: all habitable rooms other than kitchens on the ground storey, and on upper storeys a maximum of 4.5 m above ground level where served by only one stair, unless there is direct access to a protected stairway.

That is the whole reason a survey sheet lists which apertures are escape windows. Fit a smaller opener into an escape aperture and the compliance failure is structural to the job, not a snag. Name the escape apertures on the invoice.

Deposits and stage payments for made-to-measure units

A window fitter's cash flow problem is specific. You pay a fabricator for frames cut to one customer's apertures weeks before you earn a penny of fitting labour, and those frames are worthless to anyone else. That is what the deposit is for, and it is why the paperwork has to be tight.

Use recognisable stages so the customer can see what they are paying for.

The VAT treatment of the deposit is not optional. VAT Notice 700 paragraph 14.2.3 states that most deposits serve primarily as advance payments and create a tax point when you receive them. A refundable security deposit for hired goods is different, but a window deposit is not that: it is part payment for a supply. Paragraph 8.13.1 adds that VAT is due on all charges, deposits and fees which are full or part payments for a supply, that a retained payment for goods or services the customer fails to take up still carries VAT on the amount paid, and that the payment cannot be reclassified as outside the scope of VAT if the supply is unfulfilled. If you refund it, you reclaim the VAT in your next return.

For the wider contract, Notice 708 section 23 provides the framework. Paragraph 23.1.1 gives the single-payment position: the basic tax point is the date the service is performed, but if you issue a VAT invoice or receive payment before that, the actual tax point is the earlier of those two. Issue a VAT invoice within 14 days after the basic tax point and the invoice date becomes the tax point. Paragraph 23.1.3 handles the more common window-firm arrangement: where the contract provides for periodic or stage payments in the course of construction, alteration, repair or maintenance of a building, the tax point is the earlier of receipt of payment or the issue of a VAT invoice, and there is no basic tax point on completion unless the anti-avoidance rules in section 24 apply.

Practically, that means a VAT-registered window fitter should raise a numbered VAT invoice for every deposit and stage as it happens, rather than one invoice at the end covering money taken three months earlier. The template and worked wording sit in the deposit invoice template UK guide.

InvoiceAdept Free allows five invoices a month. A single window job with a survey fee, a deposit, a delivery stage, a balance and one variation is five documents on its own. Count your document volume before deciding a plan, and do not treat Free as unlimited.

Made-to-measure cancellation rights, the Consumer Rights Act and your deposit wording

Most domestic window orders are signed at the customer's kitchen table. That makes them off-premises contracts under the Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013, and the starting position is a 14-day right to cancel without giving a reason. Regulation 29 grants that right, and regulation 30 sets the clock: 14 days after the day the contract is entered into for a service contract, and 14 days after the day the goods come into the consumer's physical possession for a sales contract.

Then comes the exception that matters to every window firm. Regulation 28 sets out the circumstances excluding cancellation, and regulation 28(1)(b) removes the cancellation rights in Part 3 for "the supply of goods that are made to the consumer's specifications or are clearly personalised". Frames manufactured to a survey of one property's apertures fit that description in a way that stock double glazing sold from a warehouse does not.

Regulation 36 is the one installers get wrong most often. You must not begin supplying a service before the cancellation period ends unless the consumer has made an express request, and for an off-premises contract that request must be on a durable medium. If the service has been fully performed after such a request, and the consumer acknowledged they would lose the right to cancel once it was fully performed, the right to cancel falls away. If they cancel part-way, they pay an amount proportionate to what has been supplied, calculated on the total contract price. But if you failed to give the required information about the right to cancel or about paying that cost, the consumer bears no cost at all.

So the deposit wording on your order and your deposit invoice should do four things:

• describe the goods as made to the customer's specifications following the survey, and identify the survey and aperture schedule by reference

• state what happens to the deposit at each point: before sizes are released to the fabricator, after release, and after delivery

• record the customer's express written request for installation to begin, if that is happening inside the 14 days, with an acknowledgement of the effect on cancellation

• give the cancellation information, because failing to give it is what turns a proportionate charge into nothing at all

Do not paste that as a wall of legalese onto the invoice. Reference the order terms by clause number and keep the signed order in the file.

Alongside cancellation sits quality. The Consumer Rights Act 2015 treats every contract to supply goods as including a term that the quality is satisfactory, judged against the standard a reasonable person would consider satisfactory taking account of the description, the price and all the other relevant circumstances. Section 9(3) spells out the aspects: fitness for the purposes such goods are usually supplied for, appearance and finish, freedom from minor defects, safety and durability. Section 9(4) also matters to installers: the term does not cover anything specifically drawn to the consumer's attention before the contract was made, which is exactly why a pre-existing lintel problem or a bowed reveal should be written on the survey sheet and referenced on the quotation.

For the fitting itself, section 49 treats every contract to supply a service as including a term that the trader must perform it with reasonable care and skill. Appearance and finish, freedom from minor defects and reasonable care and skill are the three phrases most window snag disputes turn on. A dated snag list with an agreed closure date is worth more than any disclaimer.

Variations: non-standard apertures, spec changes and access

A window survey freezes sizes at one moment. Then the strip-out reveals what the brickwork is actually doing. Record every change before it becomes a disputed final balance.

Show the arithmetic plainly: original contract value, plus approved variations, less deposits and stages already paid, equals balance due. If a change reduces scope, issue a credit or a negative line rather than quietly leaving the original total in place. A customer who can trace every number from the quote to the final figure pays. A customer who has to reverse-engineer your total argues.

Where the variation was caused by something you flagged at survey, cite the survey note. Where it was caused by something nobody could have seen until the old frame came out, say that too, and attach the photograph. "Brickwork tolerance found on strip-out, photographs attached" is a defensible line. "Extra work" is not.

Scaffolding, access, waste, CDM 2015 and retention

Access and waste are real costs on window work, and both are commonly buried inside a lump sum where they cause arguments later.

Household waste electrical rules do not bite on window work: frames and glazing are construction waste, not electrical equipment. What does bite is the waste transfer paperwork for the old frames and glass, so keep the ticket and reference it if the customer asks what happened to their old windows.

CDM 2015. Most domestic window jobs are not notifiable. Regulation 6 of the Construction (Design and Management) Regulations 2015 makes a project notifiable only where the construction work on the site is scheduled to last longer than 30 working days and have more than 20 workers working simultaneously at any point, or to exceed 500 person days. A six-window replacement over three days with two fitters is nowhere near either threshold. A window replacement programme across a housing block might be, and then the client must give written notice to the HSE before the construction phase begins.

Domestic clients still matter even when a project is not notifiable. The HSE's domestic clients guidance explains that a domestic client is any individual having construction work done on their own home, or a family member's home, not as part of a business, and that the client duties normally pass to the contractor on a single-contractor project, or to the principal contractor where more than one contractor is involved. In practice, on a straightforward window job, that means the duties land on you, and the HSE notes this "should involve little more than what they normally do in managing health and safety risks". Your invoice is not the place to discharge those duties, but if you have priced edge protection, a construction phase plan or a specific access arrangement, name it as a line so nobody treats it as a freebie.

Retention. Commercial glazing and curtain-walling packages often carry retention: an agreed percentage withheld until a later trigger such as practical completion or the end of a defects period. Notice 708 paragraph 2.1.1 confirms you apply the same VAT rate to retention payments as to the earlier payments under the contract, and paragraph 23.1.2 sets out that special tax point rules apply to the retention element rather than the ordinary basic tax point.

Never put retention wording on a domestic invoice unless the customer's own contract genuinely provides for it. A householder holding back money because "the neighbours' installer did it" is not retention. That is a late payment problem, and it is handled differently.

Worked examples A to F

Every figure below is illustrative only. The arithmetic exists to show invoice layout, not to state UK market rates.

Example A — householder, six replacement windows, 20% VAT

A VAT-registered fitter replaces six casement windows in a lived-in semi. Private householder, so no CIS and no reverse charge. Self-certification through a designated scheme.

The arithmetic runs £6,798.00 + £1,359.60 = £8,157.60, less £2,500.00 = £5,657.60. Note what the invoice also carries: the aperture references, the fitting dates, the escape apertures, the ventilator provision by room and a line confirming the installation was lodged for certification. No CIS wording, no reverse-charge wording. The deposit's own VAT tax point was dealt with when it was received.

Example B — the deposit invoice for the same job

Wording on the face of the deposit invoice: "Deposit received 12 Aug 2026 against order Q-4180. Frames are made to your specification following the survey of 8 Aug 2026 and are not stock goods. See order terms clauses 4 and 9 for the cancellation position and clause 11 for the certification route. Certificate to be lodged with the scheme after completion." That single paragraph does more work than any late-payment threat.

Example C — main contractor pays the fitter, CIS 20% and reverse charge

Both businesses are VAT and CIS registered. The fitter is verified at 20%. The contractor bought the frames and free-issued them. The contractor has not made an end user notification, the work is standard rated, and the reverse charge applies.

The arithmetic is £7,230.00 − £1,328.00 = £5,902.00. The £1,446.00 is stated so the contractor can account for it, but it is not added to the payment. The invoice carries the wording "VAT Act 1994 Section 55A applies — customer to pay the VAT to HMRC". The free-issue frames are noted for clarity and are not claimed as materials, because CISR15060 does not allow a materials deduction for items the subcontractor did not pay for. The hired tower is included in the materials figure on the basis of CISR15090, which permits hired plant to be treated as materials. This is an illustration of the arithmetic, not a determination of CIS or VAT status for every contractor arrangement.

Example D — variation for a non-standard aperture

Both variations reference a written approval date and the evidence held. Neither is described as "extra work". If the customer had instead cancelled the upgrade to W4 after the frame was already released to the fabricator, the invoice would need a credit line and a plain explanation of the manufacturing cost already committed, supported by the order terms.

Example E — supply and deliver frames only, outside CIS

Face-of-invoice note: "Supply and deliver only. No installation." CISR14220 puts manufacture and delivery of glazing materials and doors outside CIS, and a pure goods supply does not meet the construction reverse-charge tests. If installation is later added under the same contract, revisit the position rather than keeping an outdated "supply only" label on the file.

Example F — commercial package with retention

A VAT-registered fitter invoices a shopfitting contractor for a replacement window package. Reverse charge applies, the fitter is verified at 20% for CIS, and the contract provides for 5% retention.

The arithmetic is £22,710.00 − £1,135.50 = £21,574.50, then £21,574.50 − £1,806.90 = £19,767.60. Retention release is diarised against practical completion. The scaffold hire and the erect/dismantle labour appear as separate lines: the hire is standard rated and outside CIS on its own, while a combined hire-plus-labour contract for standard-rated construction work goes through the reverse charge in full. That split is what makes both the VAT and CIS positions defensible on a single document.

Late payment: base rate plus eight, and the fixed sums

Put an actual due date on every invoice. Then be clear about which late-payment regime you are in, because window firms invoice both households and businesses and the two are not the same.

The Late Payment of Commercial Debts (Interest) Act 1998 is a business-to-business regime. It does not give you an automatic statutory right against a private householder. Where it does apply, two things flow.

Statutory interest is set by the Late Payment of Commercial Debts (Rate of Interest) (No. 3) Order 2002, and the drafting is more precise than most guides admit. Article 4 sets the rate at 8 per cent per annum over the official dealing rate in force on 30 June for interest which starts to run between 1 July and 31 December, or on 31 December for interest which starts to run between 1 January and 30 June. It is a fixed reference rate for the half-year, not a rate that moves with every Bank of England decision.

The Bank of England's Bank Rate page shows Bank Rate at 3.75%, held at the July 2026 meeting on 30 July 2026, and the MPC dates page shows the next decision due on 17 September 2026. Bank Rate stood at 3.75% on 30 June 2026, so for a qualifying commercial debt where interest starts to run between 1 July and 31 December 2026, the statutory rate is 3.75% + 8% = 11.75% a year. Recheck the reference rate before you assert a figure on a later invoice, or simply write "base rate plus 8%" and calculate it when you need it.

On top of interest, section 5A of the 1998 Act entitles the supplier to a fixed sum once statutory interest begins to run.

Section 5A(2A) adds a point often missed: where your reasonable costs of recovering the debt are not met by the fixed sum, you are entitled to the difference as well.

Do not paste any of that onto a consumer window invoice. For households, rely on fair terms agreed before the work, a clear due date, and proportionate reminders. Escalation and process are covered in how to chase late invoice payments.

Making Tax Digital means records, not filing

Numbered invoices, deposit tax points, variation approvals, fabricator invoices and CIS deduction statements are exactly the sort of digital records that make quarterly reporting survivable. They do not submit themselves.

GOV.UK's guide to using Making Tax Digital for Income Tax sets out what the regime actually is: creating and storing digital records of self-employment and property income and expenses, sending quarterly updates, making adjustments, and then submitting a tax return through compatible software. The quarterly updates are in addition to the return, not instead of it. Keep VAT business records for at least six years under Notice 700/21.

InvoiceAdept creates and stores invoice records. It does not file VAT returns, CIS300 returns, MTD updates or Self Assessment, and it does not decide your VAT rate or your CIS status. Export or share the records with your accountant or your filing software.

How InvoiceAdept fits a window fitter

The value of software on a window job is not clever tax logic. It is consistent numbering across a deposit, a balance and two variations, saved customer and site data so the installation address is right on every document, and a stage history you can read six months later when the retention or the certificate query lands.

You can separate frames, hardware, vents, labour, access, waste, deposits and variations; send the PDF; and take Stripe payment where enabled. InvoiceAdept adds no platform fee on top of Stripe, though Stripe's own fees apply. See pricing, CIS invoice features and VAT invoice features.

What it does not do is worth stating plainly. It does not decide who is a CIS contractor, verify a subcontractor, submit a CIS300, choose your VAT rate, file MTD updates, or issue a FENSA, Certass or Building Control certificate. The template on this page works in any system. If you are also thinking about pricing, marketing and scheme membership rather than just paperwork, start with running a window fitting business in the UK.

Mistakes that bounce window fitter invoices

FAQ

Is fitting replacement windows within CIS?

When a contractor pays you to do it, yes. CISR14020 confirms that construction operations include alteration and repair of buildings, and CISR14220 places "installation of manufactured items under 'supply and fix' arrangements" inside the scheme. When an ordinary private householder pays you directly, CIS does not apply at all, because a householder is not a CIS contractor: send a normal numbered invoice with a clear due date. VAT may still apply if you are registered, but VAT and CIS are separate systems and neither depends on the other.

Are supply-only window frames within CIS?

No. CISR14220 expressly excludes the manufacture and delivery of glazing materials and of doors from the scheme. Write "supply and deliver only, no installation" on the face of the invoice. If fitting is later added under the same contract, CISR14020 can bring the whole contract in through the installation element.

What VAT rate do I charge on replacement windows?

If you are VAT-registered, normally 20%. VAT Notice 708 paragraph 2.1 states that work to an existing building is normally standard-rated. Zero rating is limited to services in the course of constructing a qualifying new building under section 3, and 5% is limited to qualifying conversions under section 7 and properties genuinely empty for two years under section 8.

Can I charge 5% VAT because new windows save energy?

No. Energy efficiency does not by itself create a reduced rate for replacement windows. What Notice 708 does say, at paragraphs 7.6 and 8.4, is that where a job already qualifies for the 5% rate as a conversion or an empty-property renovation, improvement work to the fabric including "the installation of double glazing" can take that reduced rate too. The relief attaches to the qualifying project, not to the product.

Do I have to give the customer a FENSA certificate?

Only if you are registered with a scheme designated for that work and the job is within its scope. Schedule 3 paragraph 10 of the Building Regulations 2010 lists the designated bodies for replacement windows, rooflights, roof windows and doors in existing dwellings, including Fensa Limited and CERTASS Limited. GOV.UK says a registered installer's certificate should reach the customer within 8 weeks of completion. If the job is outside scheme scope, such as a conservatory, a porch, an extension or a new build, agree the Building Control route in writing before you take a deposit.

What U-value do replacement windows have to meet?

Table 4.2 of Approved Document L, Volume 1 sets a maximum of 1.4 W/(m²·K) for windows in existing dwellings, or Window Energy Rating band B as a minimum. Rooflights are 2.2. Doors with more than 60% of the internal face glazed are 1.4 or Doorset Energy Rating band C. Paragraph 4.8 also requires a replacement element to be no worse than the element it replaced. Where the character of the building prevents compliance, paragraph 4.10 offers a centre-pane U-value of no more than 1.2 W/(m²·K), or single glazing supplemented with low-emissivity secondary glazing.

Do replacement windows need trickle vents?

Under Approved Document F, Volume 1 paragraph 3.14, if the existing windows had background ventilators the replacements should have them too, no smaller than the originals and controllable automatically or by the occupant. Where the original sizes are unknown, or the existing windows had none, paragraph 3.15 gives minimum equivalent areas of 8,000 mm² for habitable rooms and kitchens and 4,000 mm² for bathrooms, reducing to 4,000 mm² in habitable rooms where the dwelling has continuous mechanical extract ventilation.

Can I keep a deposit if the customer cancels a made-to-measure order?

The starting point is favourable, but it depends entirely on your paperwork. Regulation 28(1)(b) of the Consumer Contracts Regulations 2013 removes the Part 3 cancellation rights for goods made to the consumer's specifications or clearly personalised. That has to be matched by clear contract terms, a survey record showing the sizes were bespoke, and the required pre-contract information. VAT-wise, Notice 700 paragraph 8.13.1 confirms VAT is due on a retained deposit and cannot be reclassified as outside the scope because the supply was unfulfilled. Take advice on a specific dispute rather than relying on a template.

When does the reverse charge apply to my window invoices?

When you and your customer are both UK VAT-registered, the payment is reported within CIS, the supply is standard or reduced rated, the customer has not notified you in writing that they are an end user, and the construction element is more than 5% of the supply value. Never apply it to a private householder or to zero-rated new build work. Use one of the accepted forms of words, such as "VAT Act 1994 Section 55A applies".

Is a window job notifiable under CDM 2015?

Rarely, for a normal domestic replacement. Regulation 6 makes a project notifiable only where the work is scheduled to last longer than 30 working days and have more than 20 workers on site simultaneously, or to exceed 500 person days. Client duties on a domestic job still pass to the contractor, or the principal contractor where there is more than one, under the HSE's domestic clients guidance.

What late payment interest can I charge a commercial customer?

For a qualifying commercial debt, 8 percentage points over the reference base rate, plus a fixed sum of £40, £70 or £100 depending on the debt size under section 5A of the Late Payment of Commercial Debts (Interest) Act 1998. The reference rate is the official dealing rate in force on the preceding 30 June or 31 December, not the live rate. Bank Rate was 3.75% on 30 June 2026, so interest starting to run in the second half of 2026 is 11.75% a year. None of this applies automatically to private householders.

Does InvoiceAdept file my CIS or VAT returns, or issue certificates?

No. It creates and stores invoices and stage records. CIS invoice features sit on Pro+ at £12.99 excl VAT, Pro is £7.99 excl VAT with WhatsApp send, and Free covers five invoices a month. It does not file CIS300, VAT returns, MTD updates or Self Assessment, does not decide tax status, and does not issue FENSA, Certass or Building Control documents.

About this guide

This guide is for UK window and door installers, glazing subcontractors and fenestration firms invoicing replacement window work. Last reviewed 3 September 2026.

Sources used and checked on that date: GOV.UK's invoice particulars, VATREC5010 and Notice 700/21 for invoice and record requirements; when to register for VAT for the £90,000 threshold; the CIS contractor guidance and deduction rates; HMRC manuals CISR14020, CISR14100, CISR14210, CISR14220, CISR15060 and CISR15090; VAT Notice 708 and VAT Notice 700; the reverse charge guidance and technical guide; Schedule 3 to the Building Regulations 2010 and GOV.UK's building regulations approval and competent person scheme pages; FENSA and Certass; Approved Documents L, F, K and B; the Consumer Contracts Regulations 2013 and Consumer Rights Act 2015; CDM 2015 regulation 6 and the HSE's domestic clients guidance; section 5A of the Late Payment of Commercial Debts (Interest) Act 1998 with the rate of interest order; and the Bank of England's Bank Rate and MPC dates pages.

Building Regulations guidance in this article is for England. Wales, Scotland and Northern Ireland have their own regimes and their own certification arrangements, so check the position for the country you are working in. Tax treatment turns on the contract, the customer, the building and the evidence. Check the current GOV.UK text and take professional advice on uncertain facts. This is not tax, legal or Building Regulations advice, and the worked numbers are not market prices.

Related templates and guides: glazier invoice template for pane repair and emergency glazing, kitchen fitter invoice template, builder invoice template, and the general walkthrough in how to invoice a client as a UK tradesperson.

InvoiceAdept is invoicing software from Tech Me Today Ltd, Companies House 15917255, ICO ZB944663. Start with the invoice generator or compare pricing. Free: five invoices a month. Pro: £7.99 excl VAT. Pro+: £12.99 excl VAT with CIS. WhatsApp send on Pro. No InvoiceAdept platform fee on Stripe; Stripe's own fees apply.