A voucher is generally obtained following a product return and can be used for 1 year from the date of creation.
Once logged in, it will be available at the "Basket" stage.

If the amount of your voucher is greater than the total amount of your order (including shipping costs), the remaining amount will be available for a future order.

If the amount of your credit is less than the total amount of your order (including shipping costs), you can place an order by completing the amount by credit card or PayPal.