OK, that's helpful to know! So basically they would need to write a letter saying they don't accept the letter of confirmation. Do I post that on to you or does it need to be them directly that post it? To what postal address? Would you accept a scanned letter sent by email or a direct email from them confirming this? If email is ok, where does it need to be sent?
Thank you for your reply but as I said in my original question, the tax body in Slovenia that I need to submit this to won't accept the letter of confirmation and asks explicitly for a certificate of residence and that article 4 be mentioned. The route you suggested won't issue me with a document that they are willing to accept.
I live and work in the UK and I am a tax resident here but my country of citizenship requires the HMRC Certificate of residence in order not to tax me on my UK income. According to HMRC guidance, you can only apply for a Certificate of residence if you receive income from both the UK and another country, but all my income is from the UK. HMRC's logic (as far as I understand) is that you don't need this certificate if you have no foreign income becuse the certificate is intended to claim tax relief on foreign income. However, I need the certificate in order to claim tax relief on UK income in my country of citizenship in accordance with article 4 of the DTA. They've asked me for CoR specifically, and won't accept the Letter of confirmation of residence, because that explicitly states that it's not for DTA purposes. Any ideas how I can proceed?