Ths is the sort of thing which could probably only ever be solved, in the long term, if everyone reciving such HMRC demands were to decide to boycott them. The way tax is spent in this country is disgraceful, the more they collect the less public services (of kinds which actually work) the state actually provides, they just find ways to burn money on ever more lumbering bureacracies, the NHS is a great example of how dysfunctional this becomes. That is on top of the fortunes of money wasted on over-reacting to the covid pandemic, which could have been handled cheaply in a civil-liberties-repecting way by copying Sweden (who were infact themselves copying the UK's pre-2020 plan). And the fortunes of money wasted by making taxation more intrusive, so they monitor more and more things, yet the salaries of all the extra bureacrats positioned to interfere with small businesses (while letting multinationals get away with anything) probably outweigh the extra tax collected anyway. One person alone would struggle to achieve anything, but a boycott by every potential payer of a tax, that isn't already taken via PAYE, would send a good message. Afterall, it was a tax boycoot that started the process that lead to the signing of magna carta.
P.S. political rant over... I noted this is a Faringdon thread, I do find the title a bit irrelevant. I opened the thread thinking it was going to be a discussion of electronics business, in practice it is a discussion of tax problems which was enough to inspire my short rant. Why didn't he title the thread "HMRC tax problems" or equivalent, with "HMRC" or "tax" in the title, in which case I'd probably never have visited the thread at all. His problems may have relation to business problems, but definitely nothing electronics specific. Oddly enough he forgot to mention switched mode power supplies this time, surprising.