Readers’ forum: Is there extra VAT on meal deals following HMRC’s brief?

My client trades as a food and drink retailer. He offers a ‘meal deal’ that includes a sandwich packet of crisps and a cookie. The cookie and sandwich are zero rated but not the crisps so this is a mixed supply for VAT purposes.

He has always apportioned output tax according to the cost price of each item – based on supplier invoices – but I understand that he must now carry out calculations according to the ratio of individual selling prices under new HMRC rules (Revenue and Customs Brief 2/23 issued on 3 March 2023). As he makes a higher mark-up on the crisps than the sandwich and cookie this will produce a higher output tax liability on each sale. I have three questions:

• Does the new HMRC guidance have the force of law?
• Does my client need to review his VAT returns for the last four...