I know most of you will know this but thought it worth mentioning just in case.
Just come across a case in practice.
Yes and any changes you while the check is taking place,you will have to write to the officer who will apply the changes to the tax return. Needless to say expect an explanation.
Here's one for you. Client paid right amount of tax to what should have been shown on their tr. However for whatever reason pension details were left out. Hmrc opened an enquiry stating expected income, but refunded client tax paid while enquiry was open. Then closed enquiry and demanded the refund back. All could have been avoided if they hadn't issued a refund during an enquiry!