If you have made an error in a claim that has resulted in an overclaimed amount, you will be required to pay this back to HMRC.
You can tell HMRC about an overclaimed amount as part of your next claim. When making your claim, you will be asked whether you need to adjust the amount down to take account of a previous error. Your new claim amount will thus be reduced to reflect this. No further action is required, but you should keep a record of this adjustment for six years.
If you have made an error that has resulted in an underclaimed amount, you should contact HMRC to amend your claim. As you are increasing the amount of your claim, HMRC will need to conduct additional checks.
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