Ok, I will need to file a paper self-assessment again this year, as I owe some tax to HMRC for 2019/20 for my US Social Security income. Please correct the following if it is not accurate.
1) I have to file the paper self-assessment by 31 October 2020. As we will be, unless things change remarkably, back in the USA by then, I will file it before we leave using tracked mail.
2) I have until 31 January 2021 to pay the taxes due. As it's not a big enough amount to trigger the "pay and balancing" scheme, I can just send the whole amount at once, as long as it's before 31 January.
3) HMRC will not take a personal credit card. They will take a debit card (for an extra fee?) or a paper check. Would it be reasonable to pay what I think I owe by check in advance so as to have that out of the way and not have to remember to do it later? As I understand it, I can't send the check with the self-assessment as it has to go to a different mailing address.
4) I also need to file a form advising HMRC that I am leaving the country. I assume I can put that form in with the self-assessment form before I go? That would stop them expecting any future self-assessments from me? (I will not owe taxes for 2020/21.)
5) That will be the end of my interactions with HMRC.
Thanks, all.