Soldato
WRT how this might manifest, I suspect that all the relevent account holders will get a "you must submit an SA this year" letter for the tax year 23/4 (it's a bit late for 22/3). There will be some form of flag that means they expect you to submit something in the relevant section, so for reduced stress you can start getting your books in order now ahead of that letter and set up a Govt Gateway account.
SA online is very easy.
SA online is very easy.