SSP, which runs WH Smith’s franchises in railway stations and motorway service stations, also owns café chains Caffè Ritazza and Upper Crust, and runs franchises for Starbucks, Burger King and Marks & Spencer’s Simply Food stores.
The company runs dual pricing at several stores, because VAT is charged on food eaten on premises, whereas it is not charged for takeaways.
Dixons and Boots, which have also come in for criticism for not offering VAT discounts and instead keeping the extra cash themselves, reissued guidance to their staff.
They reminded employees that customers are not obliged to show their boarding passes, after thousands of passengers refused following this week’s revelations.
This stance defies protests among travellers, after revealed last weekend that people are not obliged to hand over their boarding passes at airport store checkouts – and that many shops are using the information to pocket extra money when they do not need to pay VAT.