I remember moving from self employed to working for an American oil company. Their tax is complex and they have good accountants. I had real tax issues in the UK and no proper records, plus tax returns etc.. to do. I also owed a fair bit of tax. I was told to bring in whatever I had e.g. recpts, contracts, P60 etc… and it would be sorted out one way or another.
I placed a shoebox full of stuff with the accountants and never heard a word from the UK tax people after that, and nothing to pay. 😁