If the wrong product has been purchased and has already been marked as paid, it can be converted into a credit. This can then be used later to pay for a new product.
Step 1: Delete product
Select the customer whose product you want to convert into a credit. Click on the row containing the wrong product to display the different options. Next, click the "Delete" button.
A new pop-up window will open in which you have to select the option "Delete completely" to delete the product completely. The customer will automatically be issued with a credit equal to the value of the product.
Step 2: Add the correct product
Next, add the correct product.
Stay on the customer's page and click on the "+ New product" button.
A new pop-up window will open in which you can select a payment method that is not immediately marked as paid. You can, for example, use "Credit transfer" or "Pay later".
Then click on "Apply" to save the changes.
Step 3: Use credit as payment
The new product can now be paid for with the credit from the old product.
To do this, click on the "New payment" button in the customer profile and select the negative as well as the positive amount. If both amounts are the same (e.g. €100; -€100) the customer does not have to pay anything more. The product is considered paid for.
If the new product is more expensive than the old one, the customer has to pay something in addition. So it is best to do this only if the customer has actually paid the correct amount or the exact missing amount (here €15) was settled afterwards.
If the new product is cheaper, then the remaining amount must be returned to the customer immediately or in advance via their chosen payment method (e.g. in cash).