Portaria No. 430-A/2026/1 sets, from 14 September 2026, the unit amounts of ISP applicable to unleaded petrol and diesel on the mainland. The text specifies 431.60 and 264.02 euros per thousand litres respectively, including the road contribution.
These amounts form part of the temporary fuel-tax adjustment mechanism. They are neither a VAT rate nor the total pump price. Comparison must use the product category and thousand-litre unit employed in the text.
When comparing two supplies, the invoice difference alone would therefore be insufficient: quantities, fuel type and period must be made comparable. Since the road contribution is included in the stated amounts, adding it again would double-count that component. This reading enables a particular ISP calculation to be checked; it still does not justify attributing the entire change in commercial price to the tax decision.
Territorial scope is equally important: this publication does not justify automatically applying the same amounts to the Azores or Madeira. Finally, since the adjustment is temporary, later transactions must be checked against the legislation applicable on their date; September's amounts provide no guarantee of stability.