HMRC to press CIS contractors on wrong deduction rates from 7 October

HMRC has added a new genuine-contact notice warning Construction Industry Scheme contractors that they may be asked to review and correct their monthly returnsGOV, while two expired research notices fall off the page.

From 7 October up to and including 7 November 2026, a CIS-registered contractor may receive an email or letter from HMRCGOV where checks suggest the deduction rate reported on CIS monthly returns did not match a subcontractor's verified deduction rate when payments were madeGOV. The message will ask the contractor to review the monthly returnsGOV and consider HMRC's common-errors guidance and any additional information provided; the contractor may also be asked to correct errors and provide HMRC with further information.

Contractors who receive such a letter have a dedicated disclosure route: a form to report the underpaid tax with the calculation, give details of other correctable errors, or explain why the returns are correct if they disagree with HMRC's findingsGOV. HMRC reviews the information provided and aims to contact the contractor within 28 working daysGOV. Agents making a disclosure must be authorised to act for the business or company. The disclosure form is open to individuals, designated members of a limited liability company, trustees, representatives of an estate, officers of a company and agents. The contractor will need the business name, Unique Taxpayer Reference, the HMRC letter including its CFSS reference number, and details of any underpaid tax for the 2025 to 2026 tax year. Contractors who have not received a letter but need to change or correct a return should use the HMRC CIS online service or call the Construction Industry Scheme general enquiries teamGOV.

Two notices expired and were removed: 'Compliance check feedback', which ran to 2 October 2026GOV, and the 'Traders and intermediaries research panel survey' with Ipsos, which ran to 1 October 2026GOV. The 'Compliance support for growing businesses research' notice with Natcen, running to 30 November 2026, remainsGOV.

The new contact appears on HMRC's genuine-contact guidance. Separately, HMRC's CIS contractor monthly-return error-reporting guidance sets out the form contractors use to report underpaid tax, other correctable errors, or disagreement with HMRC's findings.