CIS monthly returns UK (2026): CIS300, deadlines, verification and deductions
CIS monthly returns UK, short answer: the contractor deducts CIS from qualifying construction payments to subcontractors and files the CIS300 return — HMRC does not “deduct 20%/30%” for you. Tax month runs 6th to 5th; file the return by the 19th; pay deductions electronically by the 22nd (or by the 19th if paying by post). Verify every subcontractor with HMRC before the first payment. Rates are usually 0% / 20% / 30% depending on verification status. Materials evidenced out of the CIS base stay outside the deduction. InvoiceAdept does not file CIS300; Pro+ only prints CIS invoice lines. Soften every edge case with HMRC CIS guidance / CISR manuals and your accountant.
This is a tight 2026 refresher for UK contractors who need deadlines, verification, materials, nil returns and inactivity — not a novel. Private householders are never the CIS contractor for work on their own home. VAT registration threshold is £90,000. Need clean subcontractor invoices? Use the free invoice generator (Free: 5 invoices; Pro £7.99 / Pro+ £12.99).
Who deducts CIS (answer first)
Under the Construction Industry Scheme, the contractor (or deemed contractor) must:
Verify subcontractors before first payment where required.
Deduct the correct CIS rate from the labour element of qualifying payments.
File a monthly CIS300 return and pay deductions to HMRC on time.
Give subcontractors payment and deduction statements.
HMRC does not sit on every payment and “take 20% or 30%” automatically. You (the contractor) calculate and withhold, then report and pay. Soften status questions with HMRC’s CIS overview and CISR manuals (e.g. CISR14100 / CISR14240 / CISR14260).
Actor | What they do | What they do not do |
|---|---|---|
Contractor / deemed contractor | Verify, deduct, file CIS300, pay HMRC, issue statements | Invent rates; skip verification |
Subcontractor | Invoice correctly; receive net after CIS (when deducted) | File the contractor’s CIS300 |
HMRC | Receive returns and payments; set verification outcomes | Deduct from your bank for every site payment |
Private householder | Pays a normal invoice for their own home | Act as CIS contractor for that home work |
InvoiceAdept | Helps print clear invoice / CIS line layouts (Pro+) | File CIS300, VAT, MTD or Self Assessment |
CIS tax month, return and payment deadlines
CIS runs on HMRC tax months, not calendar months.
Step | Rule (high level) |
|---|---|
Tax month | 6th of one month to 5th of the next |
CIS300 return due | By the 19th following the tax month end |
Pay deductions (electronic) | By the 22nd |
Pay deductions (post / cheque) | By the 19th |
Late filing / late payment | Penalties and interest can apply — soften with HMRC / accountant |
Illustrative: tax month 6 August–5 September 2026 → return by 19 September 2026; electronic payment by 22 September 2026. Always confirm live GOV.UK dates for bank holidays and your filing route.
Verification and deduction rates (0% / 20% / 30%)
Verify with HMRC before the first payment to that subcontractor (and when rules require re-verification). The verification outcome drives the rate you must use. Typical public framing:
Outcome (high level) | Usual rate on CIS labour element | Notes |
|---|---|---|
Gross payment status | 0% | Still report payments on CIS300 when required |
Registered for net payment | 20% | Most common net rate |
Unverified / higher rate | 30% | Used when verification rules push higher rate |
Do not invent a rate from a WhatsApp quote. Keep verification references with the job file. Soften — InvoiceAdept does not decide status.
What goes in the CIS base (materials out)
CIS usually applies to the labour / construction operations element. Materials evidenced and properly excluded stay outside the CIS deduction base. Split invoice lines so labour and materials are clear for the contractor’s AP and CIS calculation. Vague “works as agreed £12,000” lumps make materials exclusion harder to defend.
Element | Typical CIS treatment (high level) |
|---|---|
Labour / construction operations | Usually in the CIS base when the scheme applies |
Materials with evidence | Usually out of the CIS base when properly evidenced |
VAT | Separate from CIS; reverse charge is a different question |
Householder domestic job | Usually no CIS — householder is not the contractor |
Nil returns and inactivity (from 6 April 2026)
If you are within CIS but made no payments in a tax month, you may still need a nil return unless you have told HMRC you are inactive. From 6 April 2026, inactivity / nil-return practice matters more for contractors who stop paying subcontractors for a stretch — confirm the live GOV.UK / HMRC process with your accountant rather than assuming silence is safe. Soften: this page is not filing advice.
Situation | Practical cue |
|---|---|
Payments in the tax month | File CIS300 with payment / deduction detail |
No payments, still in scheme | Often need nil return unless inactive |
Stopped engaging subcontractors | Consider inactivity notification per HMRC rules from 6 Apr 2026 |
Restarting payments later | Re-check verification and filing duties before first payment |
Householders, VAT and deemed contractors
A private individual paying for work on their own home is not the CIS contractor for that job. Do not put CIS deduction narrative on ordinary householder invoices. VAT registration is separate: threshold £90,000 (£85,000 is stale). Domestic reverse charge never applies to a householder. Deemed contractor framing on construction spend is often discussed at £3 million — not £1 million. Soften with HMRC / your accountant.
Topic | Practical rule |
|---|---|
Householder own-home work | Usually no CIS; never treat them as CIS contractor |
VAT threshold | £90,000 |
Deemed contractor spend framing | £3 million construction spend — not £1 million |
Invented 0% VAT on domestic labour | Do not invent; soften Notice 708 |
InvoiceAdept | Does not file CIS300, VAT, MTD or Self Assessment |
What InvoiceAdept does and does not do
InvoiceAdept helps UK trades raise clear invoices. Pro+ can print CIS-style invoice lines for subcontractors billing contractors. It does not file CIS300 returns, verify subcontractors with HMRC, calculate your monthly liability, or replace an accountant. Free covers 5 invoices; Pro is £7.99; Pro+ is £12.99. Build PDFs in the invoice builder.
Monthly CIS checklist (contractor)
Check | Done? |
|---|---|
Subcontractors verified before first payment | |
Labour vs materials split clear on invoices | |
Correct 0% / 20% / 30% applied | |
CIS300 prepared for tax month 6th–5th | |
Return filed by 19th | |
Deductions paid by 22nd (electronic) / 19th (post) | |
Payment & deduction statements issued | |
Nil / inactivity considered if no payments (esp. from 6 Apr 2026) |
Common mistakes
Mistake | Fix |
|---|---|
“HMRC deducts 20%/30% for me” | You (contractor) deduct, report and pay |
Calendar-month thinking | Use tax month 6th–5th; return by 19th |
Paying before verification | Verify first; keep the reference |
Lumping materials into CIS labour | Evidence materials out of the base |
CIS lines on householder invoices | Householder own-home jobs: usually no CIS |
Assuming InvoiceAdept files CIS300 | It does not — Pro+ prints lines only |
Stale £85k VAT / £1m deemed language | Use £90,000 and £3 million framing |
Ignoring nil / inactivity | Check rules from 6 April 2026 with your accountant |
Frequently asked questions
Who deducts CIS — HMRC or the contractor?
The contractor deducts from qualifying payments, files CIS300 and pays HMRC. HMRC does not auto-deduct 20%/30% from every site payment.
What are the CIS monthly deadlines?
Tax month 6th–5th; return by the 19th; electronic payment by the 22nd (post by the 19th). Confirm live GOV.UK for your route.
Do I verify before every payment?
Verify before the first payment (and when HMRC rules require re-verification). Keep verification outcomes with your records.
Are materials always outside CIS?
Properly evidenced materials are usually out of the CIS base. Split lines clearly. Soften edge cases with CISR / your accountant.
Is a private householder a CIS contractor?
No — not for work on their own home. Usually no CIS narrative on those invoices.
Does InvoiceAdept file CIS300?
No. Pro+ can print CIS invoice lines. Filing, verification and payment stay with you / your accountant.
What is the VAT threshold and deemed contractor figure?
VAT registration threshold £90,000. Deemed contractor construction-spend framing is often £3 million, not £1 million.
What changed around nil returns from 6 April 2026?
Inactivity / nil-return practice matters more if you stop paying subcontractors. Confirm the live HMRC process before assuming you can skip returns.
Next step
Map your tax month (6th–5th), verify before first payment, split materials out of the CIS base, file by the 19th and pay by the 22nd (electronic). Keep householder jobs off CIS. Soften status and inactivity with HMRC / your accountant. Build clear subcontractor invoices in the free invoice generator (Free: 5; Pro £7.99; Pro+ £12.99). InvoiceAdept does not file CIS300, VAT returns, MTD or Self Assessment.
Last reviewed: 15 September 2026.
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