Work out commission without an argument
Commission accrues the moment a delivery is recorded, calculated on what was actually charged, and never on free replacements.
What you do today
You work out each person's cut at the end of the month from a stack of delivery notes, and an argument follows about the replacements.
One concrete detail
Free replacements accrue no commission at all, because nothing was charged for them — paying commission on a giveaway is exactly how the sum goes wrong without anybody noticing.

If you drive the round alone this feature is worth nothing to you. The moment somebody else drives part of it, it is the difference between a clean month and a conversation nobody enjoys.
It accrues when the delivery is recorded
Not at the end of the month, and not when the shop pays. The moment a delivery is recorded, the sum is known — what sold, at what price — so the commission is known too.
Never on free replacements
When you take back damaged or expired stock and leave fresh in its place, the shop is charged nothing. That is the rule everywhere in the product.
It follows that a replacement earns no commission either, and this is the part worth stating plainly, because it is the part that quietly goes wrong when it is worked out by hand. A replacement is a cost to you. Paying somebody a percentage of it makes it a cost twice over.
Common questions
- Who can earn commission on a shop?
- Anybody on your team, set per shop, at a rate per unit sold. A shop can have nobody earning on it, which is the default.
- Is commission calculated on the delivery or on the payment?
- On the delivery, because that is when it is known what sold. A shop paying late does not change what somebody earned.