When you are trying to encourage someone to purchase something you can adjust multiple things. Price, discounts, credits for example are tools to make the economics look attractive to a customer but help you achieve you business goal of selling more at a profitable ratio.
If you want to use credits then you can use mechanisms like rebates or just simple customer credits. If you are looking at a place to administer these then you can look at trade allowance. One example is a lump sum customer deduction. The effect is that it will generate a free text invoice onto the customer account that you nominate and will show as a credit to the customer’s account.
Here is a quick overview.
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