51. Provisional payments .-Where the price to be paid for electricity by or to the Board under this Act cannot be finally ascertained until after the end of a year of account, the amount to be paid shall be ascertained as soon as practicable thereafter, but the party from whom the payment is due shall make to the other monthly payments on account of the net amounts due in accordance with estimates made for the purpose, subject to adjustment as soon after the end of the year of account as the actual liability can be ascertained.
