P85 retrospectively

Hi I’m being asked for proof from HMRC I wasn’t a UK fiscal resident in 2021. I didn’t complete a P85 as didn’t know anything about them. I didn’t enter the UK at all in 2021. Can I fill one in retrospectively and then ask HMRC to confirm by letter that I wasn’t a fiscal resident. Or is it not something that HMRC would do (confirm by letter) even if I completed the P85? Is there any other way the HMRC would confirm I wasn’t a fiscal resident? If I filled in a P85 saying i left the UK in 2020, would this be updated on my file? So in future this would be clear? Thanks

Hi James,
You will need to contact HMRC direct for assistance: Income Tax: general enquiries.
Thank you.