Personal pension not set up to claim automatic tax relief

I've recently found out that no automatic tax relief has been paid into a private pension, through no fault of anyone but the IFA who failed to inform us of this on set up. The payments date back to 2015/16 albeit minimal, income has remained in basic rate band throughout period with two years under the personal allowance (including 2022-23), what is the best method to claim tax relief? and how far can I apply backwards? If I do this via self assessment in 2022-23, it will make no difference as total income is below PA. Do I revise earlier returns or write to HMRC? If so, what address?

Hi,

As no relief has been given, you will need to write in with the evidence to show this. We can only go back 4 years. Please write tou:

HMRC,
PAYE & Self Assessment
BX9 1AS

Thank you.