Enquiries: Information: Time limits for enquiries: The 'Enquiry window'
There are strict time limits on when an enquiry into someone’s tax credit entitlement can be opened. These time limits are usually referred to as the ‘enquiry window’.
An enquiry cannot be started:
Once the enquiry has been started there is no statutory restriction on the length of time it can last, but the claimant has the right to ask us to close the enquiry, see CCM16090.