Dozens of air travelers are refusing to show their boarding passes at airport shops in the UK after figuring out why they are being asked to show them. UK’s daily Independent revealed on Saturday that the information is used by stores to avoid paying VAT without passing on the discount to customers.

Passengers had believed that they had a legal obligation to present their boarding passes but were astonished when they realized that the inconvenience was part of a ruse to boost profits. The vast majority of airport shops wanted to see passenger passes so as to claim back 20% VAT on goods sold to passengers flying outside the EU.

Various consumer groups spokespeople are urging duty free customers not to show their boarding passes to force the shops to cut costs for travelers.