congreve

I'm registered as a Gift Aid donor with a number of charities but need to update my address details with each one. With a couple of these I have been into their charity shops and they have said they could update my details via the till or a tablet and did not need me to fill in a form. Does HMRC expect charities to keep any evidence of the change request, such as a signed form? Or is it ok for the shop to just update the record electronically?