What is a CIS tax month?

A Construction Industry Scheme (CIS) tax month runs from the 6th of one month to the 5th of the next. The first of 2026-27 runs 6 April to 5 May 2026, with its statement due by 19 May.

Contractors work to tax months, not calendar months, because they line up with the tax year, which runs from 6 April to 5 April. The 12 tax months make up one tax year. The definition is in regulation 2 of the CIS Regulations 2005, and the deadlines below follow GOV.UK and the CIS 340 guide as checked on 16 October 2026.

The 2026-27 tax months

Where the 22nd falls on a weekend or bank holiday, CIS 340 says payment is due by the previous banking day. In 2026-27, 22 August 2026 is a Saturday and 22 November 2026 is a Sunday, so those payments are due by Friday 21 August and Friday 20 November. Payment by post is due by the 19th.

What happens in each tax month

Your statement. If a contractor takes CIS from your pay, it must give you a payment and deduction statement within 14 days of the end of the tax month, so by the 19th. It can be one statement for the month or one for each payment. The statement must show the end date of the tax month (or the payment date), the gross payment, the cost of materials that reduced the deduction, and the amount deducted.

The contractor's return. By the same 19th, the contractor must send HMRC a monthly return of every payment made to subcontractors in that tax month. Since 6 April 2026, a contractor whose business includes construction work and that has paid subcontractors before, but paid nobody in the month, must either file a nil return or have told HMRC at least 14 days before the month began that it would make no payments.

The payment to HMRC. The contractor pays the deductions to HMRC by the 22nd if paying electronically. CIS 340 says contractors whose average monthly payments to HMRC are below £1,500 may pay quarterly instead, but they must still send returns every month. The monthly return deadline guide covers the contractor side and late-filing penalties.

Why it matters when you check your statements

Your bank shows calendar months. Your statements do not. A payment on 3 June sits in the tax month ending 5 June, and one on 6 June sits in the next one. If you add up a calendar month of payments and compare it with a statement, the totals will often differ even when nothing is wrong.

The same edge matters at the end of the year. A payment on 5 April 2027 belongs to 2026-27, and one on 6 April 2027 belongs to 2027-28. When you claim your CIS back, your tax return uses the total pay before deductions and the total deductions for the tax year, so you need the 12 tax months that make it up, not 12 calendar months.

What this means for you

Expect a statement by the 19th for every tax month in which a contractor paid you under deduction. If it has not arrived by then, ask for it: GOV.UK says to ask the contractor, and to ask for a replacement if you lose one. Matching statements by tax month, not by calendar month, is the quickest way to spot a missing statement or a wrong deduction.

Steps to match your CIS to tax months

1. Label each payment from a contractor with its tax month, using the table above.
2. When each statement arrives, check its gross payment, materials and deduction against the payments in that tax month.
3. If a statement is missing after the 19th, ask the contractor for it, or for a duplicate.
4. If you cannot get statements at all, write to HMRC with your name, address, UTR, the contractor's details and the tax months you were paid.
5. After 5 April, total the 12 tax months for your tax return.

The free MTD check shows when Making Tax Digital starts for you, and the trades section has more on CIS.