Store Credit for WooCommerce

My shop relies on refundable containers: I charge 1€ (non-taxed) per container, and the customers get it back in the form of a store credit when they return the jar. Accountancy-wise, this is a debt, not a sale.
This means that when my customer uses their store credit, it needs to apply to the price incl. without altering the taxes that *I* need to declare to the authorities as a shop.
Because right now, if someone uses a 10€ coupon on a cart of 8€+2€ taxes, I end up declaring 0€ in taxes.

More info here:

https://stackoverflow.com/questions/77253966/woocommerce-managing-bottles-with-deposit-return-with-tax-inclusive-prices