I do his Tax Return with an elderly relative. Every year from about May he's messaging me about doing it and how worried he is. Doing it is agony: it's quite straightforward, but he is terribly concerned about not filling in the bits that aren't relevant, no matter how many times I tell him that he would have noticed if he had Foreign Property etc. For months after we've done it he messages at intervals that he thinks he got one of the figures wrong, despite the fact that we copied them off the relevant documents. He absolutely hates clicking on 'Submit'.
Meanwhile I have an elderly neighbour who needs to book blood tests via some app/website. That is completely beyond her, so I nip round and do it, but giving them her email address terrifies her, so I have all her appointments in my inbox and write them down for her.
How older people who don't have someone confident with all these government forms that they trust with all their intimate information, I can't imagine.