Amend Bank details for repayment

My tax return was completed via a third party software for tax year 2023/2024. I have changed my bank details and would like to amend it in the self assessment return. I cannot do it online as it was submitted through the third party, I cannot use the third party provider anymore. How can I amend my bank details for the repayment?

Hi Jeet,
If you cannot amend your bank details via your Personal Tax Account,  please write to us confirming your details at the postal address provided here - Self Assessment: general enquiries
Thank you.