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HMRC internal manual

Tax Credits Technical Manual

HM Revenue & Customs
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Decision Making: Revised decisions, considering evidence and recording of decisions: Official Error

Official error as defined at s21 of the Tax Credits Act (TCA) means where the department or someone acting on behalf of the department (specific description at TCTM09530) have made a mistake.

To allow a s21 decision to be made:

  • the new decision must be in the claimant’s favour, and 
  • the claimant must not have materially contributed to the error


  • A decision made using s21 may only be revised at any time not later than five years after the date of the decision. (Prior to 06/04/10 this read as five years after the end of the tax year to which the decision relates).
  • There is nothing in the Act which permits an ‘application for a revision’ on grounds of official error. This is consistent with the purpose of the provision; that certain errors to the detriment of the claimant can be rectified without first requiring the claimant to resort to the mandatory reconsideration or appeal process. In practice, however, a tax credit claimant (or, in the case of a joint award or entitlement, either claimant), may well ask HMRC to consider revising a decision on the basis that there has been an official error, or ‘apply’ for such a revision to be done. The request or application may or may not refer to ‘official error’. However, it is the decision maker who instigates the revision under the official error provision. This may be done in the light of evidence or representations from the claimant as part of their request or ‘application’ for a revision, or it can be done on the decision maker’s own initiative (i.e. without any prior representation from the claimant).

Difference between a s21 decision (official error) and a remittance of an overpayment under CoP26 using a remission code on the Tax Credit computer system which is titled ‘official error’ (This content has been withheld because of exemptions in the Freedom of Information Act 2000)

There is a difference between overpayments remitted under CoP26 and the true legislative meaning of official error as set out above. A revision under s21 is a new decision to replace an earlier decision on the award amount, the award period or rate of entitlement. The new decision must also be in the claimant’s favour (therefore an increase). This new decision generally reverses/amends the earlier decision that created the overpayment; hence the overpayment no longer exists. The five year time limit mentioned above applies to these sorts of decisions.

A remission of a debt under CoP26 because of HMRC error for example (This content has been withheld because of exemptions in the Freedom of Information Act 2000) does not change the decision on the award amount, award period or rate of entitlement. The overpayment still exists, however HMRC take the decision not to recover this overpayment (sometimes called a remittance). There is no time limit on a decision to remit a debt under CoP26.

Note: The definition of appropriate office at TCTM09530 is only valid for official error decisions. The definition of appropriate office for all other parts of tax credits (for example making a claim) is defined at TCTM06101