Correction letter · Construction Industry Scheme
Construction Industry Scheme (CIS) discrepancy letter
For a letter or email from HMRC to a Construction Industry Scheme subcontractor about the CIS deductions on a Self Assessment return. This page sets out why HMRC sends it, what its date means and the routes GOV.UK describes, with each source and the date it was checked.
Last reviewed 10 October 2026 · How Tax Letters checks its facts
The short answer
- What this letter is
- A letter or email about a correction HMRC has made to the CIS deductions on a Self Assessment return. The letter's own words say how to question it and by when.
- Is it a compliance check?
- HMRC's manual says: “A One to Many approach is not a compliance check.” If your letter says a check has already been opened, it is a different kind of letter, with its own page. [1]
- Why it is sent
- GOV.UK says HMRC may contact Construction Industry Scheme subcontractors where there is an error on their Self Assessment return for their CIS deductions, and that the letter or email explains why the correction has been made and what you can do if you think the information is wrong. [2]
- If it is a correction to your return
- If HMRC has corrected a Self Assessment return under section 9ZB of the Taxes Management Act 1970, the law says the correction is of no effect if the person rejects it by notice to the officer before the end of 30 days beginning with the date the notice of correction was issued. GOV.UK does not say every CIS letter is a section 9ZB correction: the letter's own words say what kind of notice it is. [3]
- Your routes at a glance
Every fact on this page comes from a source listed at the foot of the page, with the date it was last checked. All sources and dates
Why you got this letter
GOV.UK says HMRC may contact Construction Industry Scheme subcontractors where there is an error on their Self Assessment return for their CIS deductions, and that the letter or email explains why the correction has been made and what you can do if you think the information is wrong. [2]
HMRC's manual says a One to Many approach sets out what HMRC wants customers to do and why, what happens if they do or do not respond, and what follow up HMRC will undertake. So the letter's own words are the best record of what HMRC is asking about, and why. [4]
HMRC's manual tells its staff that if a One to Many letter asks people for more information or records to show their tax affairs are correct, HMRC must either open a compliance check or make clear that, where information is asked for voluntarily, there is no obligation to provide it. [4]
The reply date, and what follows
What follows if nobody replies is for your letter itself to say. GOV.UK publishes what one campaign's letters say happens without a reply: for its 2026 letters to companies about Marginal Relief, HMRC says that if you do not respond, it may take further action, including opening a compliance check. For your letter, its own words are what count. [5]
What HMRC's own guidance says about disclosure and penalties: HMRC's factsheet CC/FS7a calls it an unprompted disclosure when you tell HMRC about an inaccuracy before you have any reason to believe it has discovered it, or is about to. Telling HMRC at any other time is a prompted disclosure. The same factsheet says the minimum penalty for an unprompted disclosure is lower than the minimum penalty for a prompted one. HMRC's guide to voluntary disclosure says any penalties it charges on outstanding tax will usually be lower if you tell HMRC about it yourself. [6] [7]
For an inaccuracy in a return you sent, HMRC's factsheet CC/FS7a gives the ranges: CC/FS7a gives the penalty range for a careless inaccuracy as 0% to 30% where the disclosure was unprompted, which means you told HMRC before you had any reason to believe it had found the inaccuracy or was about to. Where the disclosure was prompted, which means at any other time, CC/FS7a gives the range for a careless inaccuracy as 15% to 30%. The penalty is a percentage of what HMRC calls the potential lost revenue, the amount that arises from correcting the inaccuracy. GOV.UK: penalties for inaccuracies, CC/FS7a [6]
Your routes
Nothing to declare
If your tax is already right, your letter's own words say whether and how to tell HMRC so.
Amend a recent return
A Self Assessment return can be amended within 12 months of the statutory filing deadline. [8]
A voluntary disclosure
HMRC's guide sets out the ways to make a voluntary disclosure, including the digital disclosure service for Income Tax, Capital Gains Tax and other taxes, and says that people who qualify for a current HMRC campaign should follow its guidance. HMRC's guide says that once it acknowledges your notification, your disclosure must reach it within 90 days of that acknowledgement, and so must your payment unless you have made payment arrangements with HMRC by that date. GOV.UK: make a voluntary disclosure [7]
These are the routes GOV.UK describes. Which one fits depends on your own affairs, and this page does not say which.
If one of these is you
You think you took reasonable care
HMRC says it will not charge a penalty for an inaccuracy if you took reasonable care to get things right but your return or document was still wrong; keeping accurate records is one way it gives of showing reasonable care. [6]
Your health or circumstances make the date hard
GOV.UK says that in certain circumstances HMRC can give you an extension to a deadline, for example if you have a mental health condition, are receiving treatment in hospital or are experiencing financial difficulties. You may need to prove why you need more time. GOV.UK: get help from HMRC if you need extra support [9] [10]
Someone else helps with your tax
You can authorise a friend, relative or voluntary organisation to talk to HMRC for you and help you fill in forms. You can also authorise an agent, such as an accountant or tax adviser, to deal with HMRC for you. [11]
Questions to take to an adviser
If you talk to an adviser, these questions keep the conversation on your letter:
- Which years and which income or gains is the letter asking about, and are they on my returns?
- If something is missing, which route fits my affairs, and why?
- What would my reply say, and which records would go with it?
- Is there anything else in those years that a reply or disclosure would need to cover?
Need help with this?
Vision Consulting Chartered Accountants and Registered Auditors, Tax Letters' founding partner, is regulated by ICAEW. Talk to them in confidence, with no obligation. [12] [13] [14]
Call 020 8554 2135How Vision handles HMRC nudge letters
You can also deal with HMRC directly, free, without any adviser. Free help: TaxAid, which says it helps “people who can’t afford to pay for help”, and Citizens Advice.
The two are connected. Tax Letters takes no referral fees.How Tax Letters is funded.
Sources
Each source is linked, with the date Tax Letters last checked it.
- HMRC Compliance Handbook CH600110: The One to Many approach, overview (checked 7 Oct 2026)
- GOV.UK: Check genuine HMRC contact that uses more than one communication method (checked 7 Oct 2026)
- legislation.gov.uk: Taxes Management Act 1970, section 9ZB (checked 10 Oct 2026)
- HMRC Compliance Handbook CH600120: What is One to Many? (checked 7 Oct 2026)
- GOV.UK: Check if a letter you've received from HMRC is genuine (checked 8 Oct 2026)
- GOV.UK: Penalties for inaccuracies in returns or documents, CC/FS7a (checked 7 Oct 2026)
- GOV.UK: Make a voluntary disclosure to HMRC (checked 7 Oct 2026)
- Taxes Management Act 1970, section 9ZA (checked 7 Oct 2026)
- GOV.UK: Get help from HMRC if you need extra support, if you need more time (checked 7 Oct 2026)
- GOV.UK: Get help from HMRC if you need extra support (checked 7 Oct 2026)
- GOV.UK: Appoint someone to deal with HMRC on your behalf (checked 7 Oct 2026)
- Vision Consulting: Contact us (checked 7 Oct 2026)
- TaxAid: About us (checked 8 Oct 2026)
- Citizens Advice: About us (checked 7 Oct 2026)