Deposit scheme and returns added to existing order

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Hello,

Here in the Netherlands we have a deposit scheme for things such as crates for cheese, bottles for drinks or a pallet for a whole bulk of orders.

I have a webshop for a supplier who sells goods which uses such deposit-items and the deposit itself is calculated in the order price as separate items. The webshop also has many returning cliënts (it's actually a private webshop for a select group of cliënts). When an order is placed and the cliënt receives it's goods by transport it usually returns empty crates, bottles and pallets with the same transport back to the warehouse.

Now the webshop owner (my client) wants to manually add these returned deposit-items to the existing order so that these are deducted from the total invoice before sending the invoice.
Ideally this would be done by adding the item to the invoice and making the numbers a negative, but as I understand it negative numbers are not allowed in the quantity of a product on the order. I can ofcourse customize that myself for it to work, but Is there a better way to handle this?

Thank you in advance and kind regards,
Teeuwis Hillebrand

Hi Nicolas,

That is the current solution I implemented and works OK for the invoice part. The downside however is that I am unable to monitor how much crates there are available in the warehouse with this construction. My wish is to have the negative quantity and the positive quantity in the order affecting the total quantity available for that product.

Or should I handle that differently?

Than you in advance for your feedback!

Kind regards,
Teeuwis Hillebrand