Correction to Self Assessment

I submitted my SA last week, but have subsequently spotted a mistake. I can't see any way of issuing a correction to this submission. Please can you advise how I can submit the correction. Thanks

Follow-up question: I submitted my Self Assessment on 31 January, but spotted a mistake now and need to amend my filing. This mistake doesn't affect the amount of tax I needed to pay. Will I face a £100 late filing penalty if: a. I amend my filing using Online Self Assessment, within 72 hours of initial submission? b. More than 72 hours has passed, and I contact HMRC to amend my filing?

Hi Theon H,

If you please follow the link it has advice on how to access the return to amend:

Self Assessment tax returns

Thank you. 

Hi Peter 9728

There would not be a penalty if the change doesnt change the tax due.

Thank you.