Concession-based fiscal regime, governed by the 1991 Petroleum Act and based on the 2007 model contract. Royalty and Petroleum Income Tax (PIT) rates are fixed and payable by the contractor. There is an additional profits tax (APT) payable on a sliding scale, linked to contractor's rate of return. First tranche of APT is defined in the law to be 25% between rates of return 15 to 20%. The second (20-25% IRR) and third (>25% IRR) tranches are negotiable. There is no mandatory state participation, but the state oil company NAMCOR may negotiate an interest as part of the licence award process.