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When to tell HMRC about mistakes on your tax return

If you have made a mistake on your tax return it's very important that you tell HMRC straight away. Even if a check has already started, you should tell HMRC about any mistakes quickly. If you don't, it may increase the amount you pay.

What happens when a check starts

HMRC will write and tell you:

• that they are starting a check
• what they are checking, for example your tax return (or part of it) or a claim you have made
• what information you need to provide
• when you need to provide it by

HMRC normally has 12 months from the date you sent in your tax return to tell you that they intend to start a check. They may have longer if you have changed your tax return, sent it in late or where the information you supplied was deliberately misleading.

Using a professional adviser

If you already have an accountant or other professional adviser, HMRC will write and tell them about the check. They will write and tell you at the same time.

You can get a professional adviser to help you at any time during the check. Your adviser will need your authority to act on your behalf. Use form 64-8 to give your adviser authority to speak to HMRC about your tax affairs.

Remember that even if you have a professional adviser, you are personally responsible for your own tax affairs. You must make sure all the information your adviser supplies to HMRC is accurate.

• Get form 64-8 to authorise your agent or adviser Opens new window

Information HMRC will ask you for

The information HMRC will ask you to provide will depend on what they are checking. You'll normally receive a letter or phone call telling you exactly what's needed.

You (or your accountant or adviser) should always be able to provide the information that your tax return was based on quickly and easily. See the link below about record keeping to make sure you keep the right information.

• Record keeping (individuals and directors)

Will you need to meet face to face?

HMRC will usually contact you by post or over the phone to ask for the information they need. If there's a lot to discuss, HMRC may ask to meet you face to face at a Tax Office instead.

If you are self-employed, HMRC may also visit you at your business premises.

You don't have to meet face to face but it will help if you do. You'll be able to explain any points that you think HMRC has misunderstood. You can ask a friend, relative or your professional adviser to be there if you want.

Time limits for providing information

HMRC will give you a reasonable amount of time to provide the information they need. You can help to end the check sooner by providing the information HMRC has asked for quickly. Let them know as soon as possible if you are unable to do so and why.

If you don't give HMRC the information they need, they may make a formal request. If you get a formal request, you must reply or you may have to pay a penalty. So it's best to help as much as you can from the start.

Asking for a check to be stopped

You can ask HMRC to delay or postpone a check at any time, for example if:

• you are seriously ill
• someone close to you has died

If you think HMRC should stop the check altogether, write to them and explain why. They may agree to stop the check. If they don't agree you may be able to challenge this decision (see the section 'What to do if you disagree with a decision' below).

Possible outcomes of a check

If nothing is wrong

You'll receive a letter telling you the check has finished. In this case there won't be any changes to your tax return or claim.

If you have paid too much tax

HMRC will change your tax return to show the correct figures and you'll get a repayment. In some cases you'll also receive interest on the amount you overpaid.

If you have tax to pay

HMRC will tell you how much you have to pay, how it's been worked out and when you have to pay it.

You may also have to pay interest (if the tax should have been paid earlier) or a penalty.

When HMRC works out whether you must pay a penalty, they look at things like:

• if you took reasonable care to pay the right amount of tax
• how helpful you have been in correcting the error
• how freely you have provided any missing information

You may be asked to pay the amount in full direct to HMRC. If so, you'll usually be asked to pay within 30 days. But if you can't pay in full, you may be able to spread the payment by agreeing with HMRC that you can pay the tax back in instalments.

If you only owe a small amount, HMRC may just include it on your next Self Assessment Statement instead.

• How to pay HMRC penalties and other miscellaneous payments Opens new window

• Problems paying HMRC: advice for businesses, individuals and tax agents Opens new window

• Understanding your Self Assessment Statement

What to do if you disagree with a decision

Sometimes you may disagree with an HMRC decision - for example, you may disagree with the amount of penalty charged.

If you want to challenge the decision, you can appeal to HMRC in writing.

• Appeals against HM Revenue & Customs tax decisions

More useful links

• How HMRC checks your tax Opens new window

• HMRC's compliance checks Opens new window

Useful contacts

• Self Assessment and your tax return