Self Assessment for Non resident individuals

I have been non resident of UK since 1999. I live permanently in Canada and pay tax in Canada. I am now a Canadian Citizen. In June 2022, I started to receive my UK State pension. I have now been requested to complete a Self Assessment for the last tax year. I have never completed a Self Assessment. The last UK Tax Return I completed was over 10 years ago. I have attempted to complete the Self Assessment online but is says I am unable to use the online software because I am non UK resident. I would like to know how to complete the Self Assessment. Is there another Form that I can use? How do I get that Form?

Hi

If this is your only UK income, there is no need to complete a tax return - Tax on your UK income if you live abroad

Thank you