In this division—
"adjusted betting tax amount" , for a betting operator, for a final period,
means—
(a) if the taxable wagering revenue of the betting operator for the final period is equal to or less than the annual threshold amount—nil; or
(b) otherwise—the amount worked out by applying the taxing rate to the amount by which the taxable wagering revenue of the betting operator for the final period is more than the annual threshold amount.
(a) the betting operator’s monthly liability for any month during the final period for which the betting operator was required under section 50 to lodge a monthly return;
(b) the betting operator’s final liability for any previous final period for which the betting operator was required under section 54 to lodge a final return.