If HMRC owe you tax, then you can give your repayment to a charity of your choice simply by filling in a form. It is an easy way to make a donation and you can use the Gift Aid to increase the value of the gift.
This is done through a scheme called SA donates, with thousands of charities taking part.
To read more about the scheme and decide which charities are taking part, visit www.hmrc.gov.uk