(5) At least two percent of oil revenue shall be allocated to the oil producing states in proportion to output produced in the state, without prejudice to the special arrangements of Abyei Area. (6) After the payment to the Oil Revenue Stabilization Account and to the oil producing states, fifty percent of net oil revenue derived from oil producing wells in Southern Sudan shall be allocated to the Government of Southern Sudan as of the beginning of the pre-interim period and the remaining fifty percent to the National Government and states in Northern Sudan. (7) A Future Generation Fund shall be established once national oil production reaches one million barrels per day. (8) All funds and special accounts referred to in this Constitution and future accounts shall be on-budget operations in accordance with the public budget. CHAPTER IV SOURCES OF REVENUE Sources of National Revenue 193 The National Government may legislate for raising revenue or collecting taxes from the following sources:(a) national personal income tax, (b) corporate or business profit tax, (c) custom duties and import taxes, (d) sea-ports and airports revenue, (e) service charges, (f) oil revenues, (g) national government enterprises and projects, (h) grants and foreign financial assistance, (i) value added tax or general sales tax or other retail taxes on goods and services, (j) excise duties, (k) loans, including borrowing from the Central Bank of Sudan and the public, (l) any other tax as determined by law. 82