Working in US for UK company

During the tax year 22/23 my son was working for a UK company but was located in the US. His salary was paid in GBP into a UK bank account and his employer was deducting PAYE. Having thought his tax liabilities were being dealt with by his company he was very surprised to receive a request to submit a Self Assessment Tax Return for 22/23 He contacted HMRC about this in December and was led to believe this would not after all be required. Nevertheless, he was sent a reminder in April to complete the return - which he missed because he is still working abroad. He has now been issued with a late filing penalty, even though it's not clear whether he needed to submit a return in the first place. Can anyone offer any advice on how to resolve this? Thank you.

Hi UKparent,
Please refer to:
Tax on your UK income if you live abroad
Thank you. 
 

Hi HMRC Admin 25 Thanks very much for your response. I have visited the page in your link and can confirm that none of the criteria where SA is required applies to my son. What do you advise he should do next? Thanks

Hi UKparent

As not UK resident he would still need to submit the tax return to ensure personal allowances are due.
He will need to use 3rd party software for the return as he cannot file online as the residence section is required.

Thank you