Online booking & payment software uses the following definitions to describe the difference between a coupon code and a voucher code when selling products and making bookings.
Coupon Code (Promo)
A coupon is used to activate a discount to reduce the price when purchasing a product or making a booking. Coupons are issued by business as part of a sales promotions to attract new customer or to get more business during quiet times.
Example of a coupon code
Use coupon code SPRING2018 to get 15% off the purchase price.
Use coupon code TENOFF to get $10 off the purchase price.
Voucher Code (Gift voucher)
A voucher is generally used as a form of payment when making an online booking. The voucher code is used for full payment instead of taking a card payment to pay for the booking.
The voucher code is obtained prior to the booking by purchasing beforehand from the business website.
For example:
A fitness business sells class session passes in bulk. A customer buys a 10 session pass and receives a voucher code. When the customer books they use the voucher for payment instead of paying the class casual rate using their card.
An art school sells 10 lessons at a discounted rate. Student purchases the lesson pack and receives a voucher code. When the student books they use the voucher for payment instead of paying the full lesson price using their card.