ESIM3700 - Undue delay: the applicable period - amounts set off against an assessment
You should check the other guidance available on GOV.UK from HMRC as Brexit updates to those pages are being prioritised before manuals.
Where a person is entitled to obtain an amount by way of repayment or drawback of excise duty paid to HMRC and submits a claim but that claim is set off against an assessment, if the assessment is subsequently withdrawn and HMRC authorise the repayment or drawback, statutory interest must be paid for the applicable period.
When determining the applicable period in these circumstances the start date will be the earlier of the date the amount was set off or the 31st day following the claim. This is the original allowable period as explained in ESIM3300. The end date will be the date the repayment or drawback is authorised. ESIM3500 and ESIM3600 also apply in these circumstances.
Paragraph 5 to schedule 3 FA2001