Must an employer pay commission to an employee on maternity leave where this was earned before they went on leave?

Yes, an employee is entitled to be paid any sum earned before the start of their maternity leave regardless of whether it is actually paid after their leave has started. The employer should pay it in the usual manner on the day it is due. For example, if an employee is not paid commission until the pay date in the month after the one in which they earned it, the employer should pay them on that date even though they are on maternity leave.

During maternity leave, employees are entitled to their contractual terms and conditions apart from "remuneration", ie normal salary or wages. Most employees who meet the qualifying conditions receive statutory maternity pay (SMP) instead of their normal salary. However, where an employee is owed pay, including commission, bonuses or performance-related pay, in relation to the period during which they were at work, they can be paid it during their maternity leave, without their SMP being affected.