Concession fiscal regime which has been simplified such that there are few remaining differences between existing licences of different vintages. Corporation Tax payable on oil and gas activities is ring fenced, preventing the taxable income of the oil and gas industry in the UK being reduced by losses from other activities. The ring fenced Corporation Tax rate is higher than the standard corporation tax rate. An additional profits tax is also payable, called the Supplementary Charge or SCT. The Investment Allowance and various value allowances exist which reduce the profits subject to SCT. Fields that received development approval before 16 March 1993 are also still liable for Petroleum Revenue Tax (PRT), in addition to CT and SCT. Royalty was abolished for all fields in 2003.