ISP tax rates on diesel and petrol will fall again through an 'extraordinary and temporary' discount of 2.6 and 1.4 cents per litre, respectively, in mainland Portugal. The actual savings for consumers will be 3.2 cents per litre for diesel and 1.7 cents for petrol, as the reduction in ISP also lowers the VAT impact. This information was provided by the Ministry of Finance on Friday, March 20. The measure concerns the Tax on Petroleum and Energy Products (ISP) and aims to mitigate the effects of the war in the Middle East on the wallets of the Portuguese people. The measure is a direct response to the fuel price hike expected on Monday. Fuel prices are set to soar again next week, with a full tank of diesel expected to cost over 100 euros.