Claiming tax relief on pension contributions for PREVIOUS tax years

Hi, I am a high rate tax payer. Through ignorance, I did not know we need to individually claim back the tax relief (higher rate tax payer) on pension contributions. I managed to do this successfully for the 2023 tax year on my self assessment, that I filed in January. But I didn't see a way to do this for the previous 3 tax years, which I believe I can still do. Is the only way I am able to do this, via phoning the 0300 200 3300 number? I have called them 10 times today, I get a message saying the average wait time is 40 minutes (based on yesterdays statistics) however 10 seconds later, it says that it's too busy to take my call and it immediately terminates the call. I have no option to hold, even though I want to. How do I get in touch, if it won't even let me hold? I do not believe I can claim for previous tax years online, can I? I'd rather not write in via the post... any solutions?

Hi,

Tax returns can be amended for up to 2 years after the due date of the tax return. For example 2021 to 2022 is due by 31 January 23, so can be amended up to 31 January 2025. Once the date has passed, you can no longer amend the tax return. Instead, you can claim Overpayment relief, if withing the allowed time frame.  
To make this claim, you must follow the guidance at:

SACM12150 - Overpayment relief: Form of claims

Incorrect claims will be rejected. Please note that for 2019 to 2020, the last date by which OPR could be claimed was 5 April 2024. For 2019 to 2020 and earlier, all time limits have passed.

Thank you.