Can vouchers be used multiple times?

Gift vouchers can be used in multiple ways.

Case 1: combine multiple vouchers.

Required setting on gift voucher type: "Validation parameters > Can be combined" is set to Yes.

In this case, the price of a single voucher is (often) smaller than the price of the reservation.
For example: a reservation is 50 euros. There is a voucher of 15 and a voucher of 20 euros.
Now both vouchers can be entered and there will be a remaining amount of 15 euros.

Case 2: allow one voucher per reservation.

Required setting on gift voucher type: "Validation parameters > Can be combined" is set to No.

For example: a reservation is 50 euros. There is a voucher of 15 and a voucher of 20 euros.
Now only the first voucher entered can count. When entering the second code, a message appears that vouchers may not be combined.

Case 3: a voucher that is fully used may not be used again.

Required setting at gift voucher level: "Reusable" is set to No.

In this case, the price of a reservation is higher than the gift voucher price. For example, 50 euros, and the voucher is 30 euros.
There is 20 euros left, which can be paid separately. The gift voucher cannot be reused.

Case 4: a voucher that is partially used cannot be used again.

Required setting 1 - configuration section: "Use completely first time" is set to Yes.
Required setting 2 - at gift voucher level: "Reusable" is set to No.

In this case, the price of a reservation is lower than the gift voucher price. For example, 50 euros, and the voucher is 80 euros.
There is 30 euros left on the gift voucher. The gift voucher cannot be reused. And the remainder expires.

Case 5: a voucher that is partially used may be used again.

Required setting 1 - configuration section: "Use completely first time" is set to No.
Required setting 2 - at gift voucher level: "Reusable" is set to No.

In this case, the price of a reservation is lower than the gift voucher price. For example, 50 euros, and the voucher is 80 euros.
There is 30 euros left on the gift voucher. When completing the reservation, the price of the gift voucher will be adjusted from 80 to 30.
After this, the same gift voucher can be used again.
When the remaining balance reaches 0, the gift voucher has been fully used.