What is the CIS monthly return deadline?

What is the CIS monthly return deadline? Your CIS monthly return must reach HMRC by the 19th after each tax month ends. Tax months run from the 6th to the 5th, so the month to 5 November 2026 is due by 19 November 2026. It must reach HMRC by 19 November 2026. The deductions are due by 22 November if you pay electronically, but that is a Sunday, so CIS 340 says to pay by the previous banking day. Since 6 April 2026, yes, if your business is construction and you have paid subcontractors before. File a nil return by the 19th, unless you told HMRC at least 14 days before that tax month started that you would make no payments in it. £100 the day after the deadline, another £200 at 2 months, then the greater of £300 or 5% of the deductions on the return at 6 months and again at 12 months. Read the full answer, with every source, at rightotax.co.uk.