The discount amounts to 10c per liter of fuel, up to 50 litres per month per person. The discount is being conducted through the IVAucher programme.
Portugal introduced the IVAucher VAT discount programme to boost its vital tourism sector. Through the programme, consumers who spend money in the hospitality sector can receive their VAT back as a credit, which can be spent on another tourism/hospitality purchase.
Source VATit
