WooCommerce & wallet & inventory management software: errors in VAT

We would like to use an internal WooCommerce shop in the following way:

• Each of our employees should receive an individual voucher (or coupon) with which they can make purchases for a specific value.
• Residual values ??should not expire, but should be able to be used later.
• It should also be possible to pay for a product by using the remaining value of a voucher and another payment source, for example PayPal.
• At the same time, it should work with the German inventory management software called JTL.

I set it up with a wallet system, which also worked perfectly with normal gross values.

However, this does not work with JTL, as JTL only transmits net prices to WooCommerce, even if gross prices are displayed to the customer. (The plugin that connects WooCommerce to JTL has a setting that automaticly configurates WooCommerce, so that both databases don’t cause issues)

I ran through 3 cases that make the problem clear (see below).

To test this, I tried two wallet plugins that dealt with the problem in exactly the same way.
So I came to the conclusion that these only work if the gross prices are stated directly in Woocommerce.

These plugins do not have the option to switch between gross and net.

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Has anyone had a similar problem or built something similar and found a working plugin for it?
Or maybe an idea how to solve this more easily, with a different solution?

The only solutions I can think of are wallet plugins or the coupon solution via Woocommerce.

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However, with coupons via Woocommerce, residual values ??would expire and you would have to create the coupons for each customer individually.

(In the wallet there was the option of either transferring an amount directly to the wallet when the account was created or assigning it later.)

Example cases:

(All orders include VAT)

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Case 1:

• Order is lower than wallet
• (for example: order for €50, with a wallet value of €100)

Works perfectly: invoice is correct, wallet billing is correct

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Case 2:

• Order is significantly larger than wallet value without VAT
• (for example: order for €150, with a wallet value of €100)

Works perfectly: invoice is correct, wallet billing is correct

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Case 3:

• Order is larger than wallet value, but order without VAT is smaller than wallet value
• (for example: order for a value between €100.01 and €116, with a wallet value of €100)

example:

• €104.50 order value (incl. VAT)
• 100€ wallet
• Pure VAT: €16.68

Result: you can pay via wallet + PayPal

But: you pay €87.82 (wallet) and €16.68 for the rest

In this case, the plugin always indicates the VAT value, which must be subsequently paid via PayPal.

It also shows in the checkout that you have used €100 from the wallet, which is incorrect.
However, it is displayed correctly in the calculation list of the cash register.

No VAT is charged in the invoice in Woo.

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