REVENUE REGULATIONS NO. 2-2000 issued January 15, 2000 prescribes the procedures to be adopted during the transition period in the phasing out of leaded gasoline in Metro Manila, as mandated in Executive Order No. 446. The transition period shall be reckoned from the day of inventory taking which will be conducted within five (5) days from the effectivity of the Regulations and shall last not more than forty-five (45) days or whichever is earlier until such time that the leaded gasoline has been diluted to unleaded gasoline. A conduct of physical inventory of all stocks on hand of leaded and unleaded gasoline stored at the refinery plants and depot/terminals in Metro Manila shall be done by the BIR, in coordination with representatives from the Department of Energy and in the presence of representative(s) of the concerned oil company. Each removal of the remaining stocks of leaded gasoline subjected to inventory taking shall be accompanied by a Withdrawal Certificate duly issued by the BIR personnel assigned on the premises of the subject taxpayers. A weekly report of inventory utilization shall be submitted to the Assistant Commissioner of the Excise Taxpayers Service on or before Tuesday of the following week, until such time that the said inventories are fully exhausted. In the event that the said stock has been completely exhausted and the remaining stock of diluted gasoline does not meet the prescribed maximum lead content of 0.013 gram per liter for unleaded gasoline, each subsequent removal of such gasoline shall be considered leaded gasoline and an additional tax of P 1.00 Peso per liter of said gasoline shall be due therefrom and shall be paid in accordance with the provisions of RMO No. 99-98. The said procedure shall continue until such time that the content of the storage tank conforms with the prescribed maximum lead content for unleaded gasoline. The first-in-first-out method of accounting shall be used in the receipt of unleaded gasoline and removal of leaded gasoline from the storage tank. After the transition period, commingling of leaded gasoline with unleaded gasoline is prohibited.