If commission is part of your salary and not an incentive, it should be included to calculate your maternity leave pay.
The amount of commission to be included in your maternity leave pay can be your average monthly commission for 6 months just before your child’s birth.
If your child’s date of birth is 1 July, then it’ll be your average monthly commission from 1 January to 30 June.
If you did not get commission in the 6 months just before your child’s birth, the average over other period can be used.