4Amount of duty
(1)Where a vehicle licence for a vehicle of any description is taken out for any period of twelve months, vehicle excise duty shall be paid on the licence at the annual rate of duty applicable to vehicles of that description.
(2)Where a vehicle licence for a vehicle of any description is taken out for a period of six months, vehicle excise duty shall be paid on the licence at a rate equal to fifty-five per cent. of that annual rate.
(3)In determining a rate of duty under subsection (2) any fraction of five pence—
(a)if it exceeds two and a half pence, shall be treated as five pence, and
(b)otherwise, shall be disregarded.
(4)Where a vehicle licence for a vehicle of any description is taken out for a period specified in an order under section 3(3), vehicle excise duty shall be paid on the licence at such rate as may be specified in the order.
(5)A rate of vehicle excise duty specified in an order under section 3(3) in relation to a licence taken out for a vehicle for a period of—
(a)a fixed number of months other than twelve, or
(b)less than one month,
shall be such as to bear to the annual rate of duty applicable to the vehicle no less proportion than the period for which the licence is taken out bears to a year.
(6)A rate of vehicle excise duty specified in an order under section 3(3) in relation to a licence taken out for a vehicle for a period of three months or a period of four months shall not exceed for each month of the period ten per cent. of the annual rate of duty applicable to the vehicle.
(7)The power to make an order under section 3(3) includes power to amend or repeal subsection (2) or (3) of this section.