Self Assessment ― amendments and corrections

By Tolley

The following Personal Tax guidance note by Tolley provides comprehensive and up to date tax information covering:

  • Self Assessment ― amendments and corrections
  • Correction
  • Amendment
  • What if the taxpayer misses the deadline to amend the Return?

Once a Self Assessment Tax Return has been filed, both HMRC and the taxpayer (or his agent) has the right to make changes to the Return. There are different time limits depending on whether it is a correction by HMRC or an amendment made by the taxpayer.


HMRC has the right to amend the Tax Return within nine months of the date of receipt (ie the date the Return was filed rather than the due date for filing) without opening an enquiry. Usually, HMRC does this to eliminate or to reverse any obvious errors or mistakes within the Return. These are usually arithmetical errors, although HMRC can reverse any technical mistakes made by the taxpayer in completing the Return.

TMA 1970, s 9ZB(1), (3)

HMRC will notify the taxpayer of any amendments made (with a copy to you as the agent). The taxpayer is not bound to accept the correction. The correction can be rejected within 30 days of the date the notice was issued by HMRC (ie not the date of receipt of the notice). If you need to reject the correction, it is suggested that you do so in writing, stating the reason(s) you believe the correction is incorrect.

TMA 1970, s 9ZB(4), (5)

If the correction is rejected and HMRC does not agree with the reason for the rejection, it is likely that the Officer will open an enquiry into the Return. See the Types of checks on returns guidance note.

For further reading, see Simon’s Taxes E1.214 (subscription sensitive).


The taxpayer also has the right to amend the Return already submitted, so long as this is within 12 months of 31 January following the end of the tax year (eg 31 January 2020 for a 2017/18 Tax Return). This is the deadline irrespective of whether the Return

More on Administration: