Appeals, postponements and reviews: reviews: time limits
Where a review has been offered by HMRC by the issue of a Decision Makers letter, the time limit by which HMRC must notify the customer of the conclusion of the review is 45 days from the date HMRC receives the review acceptance, unless a different period is agreed with the customer (see ARTG4030).
Where a review has been requested by the customer, HMRC must write to the customer within 30 days (or other reasonable time) setting out our latest view of the matter. The time limit by which HMRC must notify the customer of the conclusion of the review, is 45 days from the date of that letter (see ARTG2210).
In the exceptional event that more time is needed, this should be requested as soon as possible. Further guidance on this is in ARTG4690.