I am a UK citizen, living in the UK. I lived and worked in the USA for 15 years returning to the UK in 2006. Last year I retired and started receiving US Social Security payments from the the time that I worked in the USA. I assume I now have to file a US tax return for 2021,
My question - I have tried to determine this through the form instructions but its unclear - should this be through a standard 1040, or a 1040-NR?
