If a business has overdeclared output tax on past returns then it seems reasonable that this should be corrected, either by adjusting a current return or submitting a form VAT652 if the “error” is over £10,000 net.
If it is a genuine adjustment, surely HMRC must recognise the correction and either make a repayment or offset the overdeclaration against a current amount of VAT due.
The answer is yes, but… “unjust enrichment”…
Source: marcusward.co