The relationship between receipts and sale items is inseparable.
A sale item cannot exist without a receipt and vice versa. When you checkout, a receipt is created that contains all the sale items being checked out in that purchase. (For bulk uploads, a new receipt is created for each individual sale item to ensure this relationship is maintained).

Commission value split by payment method: on a sale item you'll notice that the Total Store commission value has a breakdown of the commission by payment type. Because each dealer can have a different store commission % per payment method, at checkout, the % split of payment methods used to pay for the receipt is used to mirror the % breakdown of commission values on a sale item.

An example:
If your receipt totalled £100, was paid for £60 by card and £40 by cash and contained 2 sale items.

Let's assume one of those sale items was worth £10, and let's assume the dealer for that sale item had a store commission card value of 5% and a store commission cash value of 3%.

Because of the payment method breakdown for the receipt, we apply that same split as the sale item level. So the 5% store commission on card is applied only to £6 of the sale items value, and the remaining £4 is subject to the store commission cash value of 3%.

This means the final sale item commission values would be:
Cash store commission: £0.30
Card store commission: £0.12
Total: £0.42

Updating a receipt will result in the totals, for each payment method, updating not only in the receipt but will also affect the payment method % split for each sale item within. So continuing the example above, if the receipt was updated so the card value actually became £55 and the cash value £45, then our updated sale item store commission split would be:

Cash store commission: £0.28
Card store commission: £0.14
Total: £0.42

Warning - if you update a receipts total value to be greater or less than the original value, this will not affect the included sale items but it certainly may cause confusion in the future when you try to reconcile the totals. We recommend, if you do choose to make such a change, that you make a note on the receipt explaining the reasoning for it. This extends to sale items as well, updating their sale price will only update the sale price itself and not the parent receipt, so add a note explaining this for your future reference.