Upstream licences are awarded under concession terms through the licensing rounds. The latest 'Thai III plus' fiscal terms were announced in 2014. Royalty rates range from 5-15% and are based on a sliding scale linked to production, with a discount applied to deepwater licences. The Special Remuneratory Benefit (SRB) is a tax with a unique calculation method. Its rates are based on the annual revenue and the cumulative metres of wells drilled in the concession area, with an adjustment for geological complexity. Corporate income tax of 50% is also payable on profits. Other fees and bonuses are also payable. In April 2018, Thailand introduced new PSC regime for the licensing round on the expiring contracts, however, these terms are not yet applicable to the new exploration licences.