56.3. A worker’s salary and wages on which a first additional contribution has been made for a year under a similar plan is equal to the lesser of(a) the amount by which the aggregate of all amounts each of which is the worker’s pensionable salary and wages for the year in respect of pensionable employment under the similar plan exceeds the proportional share of the worker’s personal exemption for the year under the plan;
(b) the proportional share of the worker’s maximum contributory earnings for the year under the similar plan; and
(c) the amount obtained by dividing, by the first additional contribution rate for employees for the year under the similar plan, the aggregate of the deductions at source from the worker’s salary and wages for the year on account of the first additional contribution under this Act or a similar plan and any amount that an employer has not deducted at source from the worker’s salary and wages for the year on account of the first additional contribution, as the employer should have done under this Act or a similar plan, provided that the worker has given notice of that fact to the Minister on or before 30 April of the following year.