How to correct a CIS return

How do I amend a CIS return online?

In HMRC’s CIS online service, the same place you file it. GOV.UK says: Use the HMRC CIS online service to change or correct something on your return. If the return has not gone yet, just change it before you send it.

1. Get the right figures together. For each subcontractor on that month’s return: the gross payment, the materials and the deduction, from your invoices and payment records.
2. Sign in to the CIS online service. GOV.UK’s CIS sign in page uses your business tax account.
3. Choose Amend return. HMRC’s guide CIS340 says to select ‘Amend return’ from the ‘Returns’ menu, then pick the tax month with the mistake.
4. Correct each wrong entry. Change the wrong figure, or add a payment you left off. The return should show what you actually paid and deducted that month.
5. Check it and send it. Check the totals against your records before you submit, and keep a copy of what you sent.
6. Give the subcontractor a corrected payment and deduction statement if the one they have shows the wrong figures. How to correct a statement

Source: CIS340 4.6, on the monthly return: it should reflect what the contractor has actually paid and deducted in the month it covers. HMRC manual CISR66010: A contractor should try and amend online in the first instance. If the mistake is spotted before sending, they may simply rectify the error by revising the information they have entered on-line, or by completing a new form CIS300.

Stuck? GOV.UK says: Tell HMRC by calling the CIS helpline if you need any help with this. CIS helpline contact details

A correction makes most sense once you know what each monthly return should hold. How CIS works walks through the monthly routine.

What can I not change in HMRC’s CIS online service?

Two kinds of return: one you sent with other software, and an out of date return.

• A return sent with commercial software. CIS340 says: You are unable to use HMRC software to amend a monthly return that was sent using third-party software. Correct it in the software you used. If the software cannot do it, HMRC’s manual says they will need to contact their software supplier.
• An out of date return. CIS340 says: To amend an out of date return, contractors must write to HMRC providing all details. The address is PT Operations North East England, HM Revenue and Customs, BX9 1BX.

If you cannot amend online at all, HMRC’s manual says you can:

• Send in a new (corrected) return
• Write in with the correct details
• Telephone the CIS helpline

Source: HMRC manual CISR66010: Alternatively, if the contractor cannot amend online, they may use one of these three ways.

How far back can I correct a CIS return?

This tax year and the previous six. HMRC’s manual says: You may correct errors on returns relating to the current tax year and the previous 6 tax years (CY-6).

That limit is in the manual HMRC’s own staff work from. CIS340, the guide written for contractors, explains how to amend a return but does not give a time limit.

Worked example: a deduction entered at the wrong rate

You pay a subcontractor for a job: £1,500 of labour and £500 of materials. Verification matched them, so you take 20% off the labour, which is £300. The subcontractor’s statement shows £300.

On the return, you enter the deduction at the higher rate of 30% by mistake: £450. That is a mistake on the return, not in the money. CIS340 describes a contractor who might make a mistake in entering details of the payment or deduction onto the return. Here is the fix:

1. Amend that month’s return. Change the deduction from £450 to £300. The gross payment of £2,000 and the materials of £500 stay as they were.
2. Check the subcontractor’s statement. It already shows £300, so it matches the corrected return and nothing changes for them.
3. Check what you paid HMRC. You owe HMRC the £300 you deducted. If you paid the £450 from the wrong return, that is £150 too much, so call the CIS helpline about it.

What if I paid the subcontractor the wrong amount?

Then the money is wrong, not just the return, and you usually put it right on the next payment:

• Paid too little. Make up the difference with the next payment, and put the deduction on that month's return rather than reopening the old one.
• Paid too much. Agree a reduced payment next time rather than asking for money back. HMRC's own example works exactly that way.
• Paid too much and the job has ended. With no next payment to take it off, CIS340 says the contractor should contact the CIS helpline to report the error.

Source: CIS340 4.8: Underpayments of this type can usually be put right by a further, balancing payment. CIS340 4.9: the contractor may agree with the subcontractor to pay £1,000, instead of the £2,000 due.

What if I did not deduct enough tax?

You owe HMRC the difference yourself. CIS340 says that where a required deduction has not actually been made from the subcontractor’s payment, the contractor is still responsible for paying that amount to HMRC.

Using the figures above: if verification had told you to deduct 30% and you took 20%, the 10% gap on £1,500 of labour is £150, and that is yours to pay.

HMRC can let you off, but only if you satisfy it that you took every reasonable care and that the failure to make all or some of the deduction was due to an innocent error (CIS340 §4.21). That is HMRC’s decision, not a given. Verifying before you pay is what stops this happening.

How do I correct a subcontractor’s payment and deduction statement?

Give them a new statement with the right figures, so it matches the corrected return. CIS340 uses those words where a payment has to be redone: the contractor should retrieve and reissue the subcontractor’s payment statement.

Wrong statements carry their own penalty. CIS340 says: We may charge contractors penalties of up to £3,000 if they negligently or deliberately provide incorrect information in such statements. What a payment and deduction statement must show

Will I get a penalty for correcting a CIS return?

Not automatically. HMRC’s guide says: HMRC recognises, however, that contractors will sometimes make mistakes on their monthly returns. Where this happens we’ll not automatically look for penalties or take away the contractor’s own gross status as a subcontractor.

Penalties are kept for the more serious cases, where we believe the error or omission has been caused by the contractor’s negligence or intent. A late return is a separate matter with its own penalties. CIS return deadlines and late penalties

Separately, from 1 April 2028, a new general duty is set to require taxpayers to correct a tax return or document once they know it is wrong (needs Parliament to pass Finance Bill 2026-27). Which returns it covers will be set out in the Finance Bill.

Other questions about correcting a CIS return