Miscellaneous income allowance and past years

Hello In addition to my salaried work I earn another £200-500 a year, which I have always declared on my SA form. I understand that there has been £1000 allowance since 2017, and that I didn't need to declare as under £1000. I have two questions please Is my understanding correct? Can I claim for previous years that I declared as I didn't use the allowance? If I can, how many years can I go back, and what would be the best way of claiming for that via the SA form? I work as a doctor and the money in question is either for cremation papers or statments for the courts Kindest regards David

Hi helidoc,
You can claim the trading allowance of £1000 per annum against self employment.
The earliest you can now go back to is 2020 and you will need to write in to claim overpayment relief .
Please see guidance here:
SACM12150 - Overpayment relief: Form of claims
Thank you.