This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

VAT Traders’ Records Manual

VAT invoice: issuing: Issue of VAT invoices by deregistered traders

You may discover that a deregistered trader has undercharged tax on a supply he made before he deregistered. To avoid having to account for any additional tax due out of his own finances, the trader may request permission to issue a VAT invoice to the customer concerned in an endeavour to recoup the tax.

You should critically examine this type of request and find out the full circumstances surrounding the failure to account for tax at the proper time. If you are satisfied that there has not been a deliberate attempt to avoid paying tax, you can advise the trader that the request has been allowed. Any underdeclaration of tax is to be dealt with in line with VAEC (VAT Assessment and Error Correction Manual. You can find further guidance on the treatment of deregistered traders in VATREG.