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HMRC internal manual

Tax Credits Technical Manual

Section 19 - Enquiry time limits

Opening an enquiry:

There are time limits for opening an enquiry.  An enquiry cannot be opened until there has been a final s18 decision.  This could be when the claimant makes a response to the s17 declaration or if there has been no response to the s17 notice it cannot be opened until after the automated s18 decision has been made after 1SD. 

If the claimant finalised with estimated income by 1SD the enquiry cannot be opened until the final decision has been made on the actual income details following the claimant’s response, or the automated s18 decision is made after 2SD. 

Once the enquiry has been started there is no statutory restriction on the length of time it can last.

The period allowed for the initiation of an enquiry is the period beginning immediately after the relevant section 18 decision has been taken.

An enquiry must be opened before one of the following dates, known as the enquiry window:

  • Where the claimant is not required to complete a tax return (most employed claimants) and has responded to the s17 notice with actual income – the enquiry must be opened by one year after the 1SD.
  • Where the claimant is required to make a tax return, the enquiry must usually be opened by one year after the date they are required to submit their tax return. This is usually by one year after 2SD There are some exceptions to when an enquiry must be opened by. Please see TCTM10230 for examples.


Closing an enquiry:  

Once an enquiry has been opened, HMRC must decide if the claimant(s) are entitled and if so, the amount that he/they are entitled to.

The enquiry will close once HMRC gives the notice of the decision on the enquiry. If HMRC gives notice to either claimant at different times, the enquiry closes on the later of those times.         


The first specified date and the second specified date are not always the 31 July and 31 January, they are linked to the issue date of the s17 notice. If the s17 notice is issued late and within 30 days of 31 July or 31 January then the relevant specified date is extended so that a minimum of 30 days is allowed for a response.