I've just spoken to HMRC who didn't accept that Gift Aid donations were not included as part of my P800 calculation. (Have been doing this for 6 years so have some knowledge of system and P800). The p800 mentioned "professional fees or subscription" but there is no mention of "charitable donations" as has been the last in all the previous p800 letters. The HMRC agent on the phone said she doesn't know why it doesn't show up in the p800 letter but she is certain that it has been included in the calculation. Wasn't able to offer any further help and asked me to write in if I disagree. Any advice on best way to go about this? Want to avoid writing in as sounds like a long-winded process. For relevance: Total taxable income 76180 professional subscriptions 1041 personal allowance 12570 total taxable income 62569 20% at 37700 - 7540 40% at 24867 - 9946 total tax should have paid - 17486 Surely, if gift aid was included this number would be lower.