This depends on the type of voucher.
Coupons that reduce the price of a specific item (e. g. Home & Living Coupons, Beauty Coupons, BLACK2021) can be combined.
Simply enter the voucher codes one after the other in the "Enter voucher code" field and confirm each entry with the "Redeem" button.
Vouchers that reduce the total amount and have a minimum purchase value (e. g. satisfaction vouchers) cannot be combined with other vouchers.