Recent upstream licences are awarded under Production Sharing Contract (PSC)-based fiscal regime, while all production licences are currently governed by older concession terms. Royalty, cost recovery ceilings and profit oil splits vary by area and hydrocarbon type, with the latter based on a sliding scale rates linked to production. Profit oil splits are biddable/negotiable, while cost recovery ceilings and royalties are set for each licensing round. Corporate income tax, supplementary payment and research contributions are payable. State companies have the right to take a working interest of up to 15% in any commercial development. Past exploration costs incurred by an IOC are reimbursed by the state from its share of production if it does exercise its right.