If you’re a contractor in the Construction Industry Scheme (CIS), you may hear from HMRC this autumn.
From 7 October up to and including 7 November 2026, HMRC may email or write to CIS contractors where the deduction rate on their monthly returns doesn’t match the subcontractor’s verified rate. HMRC lists this contact on its page of genuine HMRC contact. Here’s what they ask and what to check.
Key points
- From 7 October to 7 November 2026 (inclusive), HMRC may email or write to CIS contractors about deduction rates.
- It is contacting contractors where the rate on monthly returns doesn’t match the subcontractor’s verified rate.
- The letter asks you to review your returns against HMRC’s common-errors guidance. It may ask you to correct errors or give information.
- Common errors: the wrong deduction rate, materials not recorded separately, and incorrect figures.
- HMRC lists these letters and emails as genuine contact. If you get one, send it to us.
On this page
What HMRC is doing
From 7 October up to and including 7 November 2026, HMRC may email or write to CIS contractors where the deduction rate on monthly returns doesn’t match the subcontractor’s verified rate.
In other words, HMRC’s checks suggest the rate on your monthly returns didn’t match the subcontractor’s verified deduction rate when the payments were made. Where the two don’t match, you may hear from it.
Subcontractors: separately, from 10 August up to and including 31 December 2026, HMRC may email or write to CIS subcontractors where it has corrected an error in the CIS deductions on their Self Assessment return. The letter or email explains what was corrected and why, and what you can do if you think the information is wrong. HMRC lists this contact on the same genuine-contact page.
What the letter asks you to do
The letter or email asks you to review your monthly returns against HMRC’s guidance on common errors (HMRC’s CIS guide for contractors and subcontractors, CIS 340). It may also ask you to:
- correct any errors; or
- give HMRC information.
The common errors to check
The common errors are:
- using the wrong deduction rate;
- not recording materials separately; and
- incorrect figures.
Before each monthly return, it helps to:
- verify your subcontractors when required;
- use the latest deduction rate HMRC gives you; and
- record the cost of materials separately where materials are included on the invoice.
Is it really from HMRC?
HMRC lists this contact on its GOV.UK page Check genuine HMRC contact that uses more than one communication method. A scam can copy a real campaign, so if you’re unsure whether a message is real, don’t click any links. Forward it to us or check GOV.UK.
What to do if you get one
Don’t ignore it, and don’t guess. Send it straight to us. It helps to have your recent monthly returns, your subcontractor verification details and the invoices showing materials to hand, so we can look at them together.
Sources
Our main sources are HMRC and GOV.UK:
- Check genuine HMRC contact that uses more than one communication method
- Construction Industry Scheme: CIS 340 (guide for contractors and subcontractors)
- Agent Update: issue 147
Talk to us about your CIS returns
If you’ve had a letter or email from HMRC about your CIS returns, or you’d like a second look at how your monthly returns are prepared, we can help. Call us on 020 7164 0225, send us a WhatsApp message or email your tax enquiry to hello@ibandco.co.uk.
See also our Business Tax Advisory and payroll management services.
Checked on 9 October 2026. The Budget on 28 October 2026 may change some of these rules and rates. We plan to review this post after the Budget. Please check with us before acting.
Please note: this article is general information based on our understanding of UK tax rules at the date shown above. It is not advice for your circumstances, and tax rules and rates can change. Please speak to us before acting on it.
Ishmael Bangura FFA
Ishmael Bangura FFA is a qualified tax adviser and Fellow Financial Accountant with a finance degree and about 15 years’ experience, including earlier corporate roles. He has helped more than 950 clients. IB&Co Accountants is regulated by the IFA and IPA. IB&Co is based at Level 37, 1 Canada Square, Canary Wharf.
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