VATREC13020 | Credit and Debit notes: Legal basis for credit notes
From HM Revenue & Customs · VAT Traders’ Records Manual
Credit and Debit notes: Legal basis for credit notes
The UK Law that covers credit notes is found in Regulations 15, 15C, 24A and 38 of VAT Regulations 1995 (SI 1995/2518). Regulation 24A defines the term “increase [or decrease] in consideration”.
This is because the VAT liability is determined by the underlying supply position, not by the issue or receipt of a credit note. So when questions arise about the validity or effect of a credit note, you need to determine why it was issued and look to the law that covers the underlying position. This might be, for example the law on:
consideration;
tax value;
correction of errors; or
overpayments of VAT.