This Practice Note is about the rules on petroleum revenue tax (PRT), which was payable by oil companies on the value of oil and gas produced and receipts from the use of qualifying infrastructure, less certain costs and reliefs. PRT was charged at varying rates following its introduction in 1975. It was set at 50% from July 1993 until it was reduced to zero with effect from 1 January 2016. It is still however possible to create losses which can be carried back to recover past PRT paid. For information on the corporation tax, supplementary charge and energy profits levy rules applying to companies in the oil and gas sector, see Practice Note: Oil and gas—corporation tax, supplementary charge and energy profits levy. PRT post 1 January 2016 Under a 0% regime, losses calculated under the PRT rules arising on decommissioning or otherwise must be carried back on a last in, first out basis such that they would first have to be set against profits suffering the 0% rate, with only the excess losses being