Clef

Hi everyone, I am an Italian citizen and have lived and worked in the UK circa 2015-2017, and have moved to Denmark since. The local tax authorities are now asking for proof that I have lived in the UK during 2015-2017. I am considering of requesting a Certificate or residence, but I couldn't understand if it possible to do so retroactively (i.e. as a non-british citizen who doesn't live in the UK anymore). I have tried the online form on the HMRC website, but that seems to require identity verification specifically asking for a UK-issued document which I don't have. I have also found this form: https://www.tax.service.gov.uk/shortforms/form/PT_CertOfRes which could work for me? I would only need a letter or document that states that I was living and registered in the UK for the aforementioned period. Also, do you have an estimate of how long it would take to receive such a certificate? Unfortunately the deadline for submitting this evidence is quite tight. thank you and kind regards