Section 11. Amount payable on liability occurring for the first time

1 [ 11 Save as otherwise provided by or under this Act when, in respect of a transport vehicle, the tax becomes payable for the first time after the commencement of any calendar month, the tax payable under Section 4 shall be one third of the appropriate quarterly tax or one-twelth of the appropriate yearly tax for each calendar month or part there of in respect of which the tax is payable.]