AFAIK it needs to be used onboard. But you'll likely spend $50 onboard. All meals are included, but if you want alcohol or pop outside the dining rooms, purchase pictures, take excursions or buy anything in the shop, there will be an onboard charge. We spent a little under $700 for four days ($85 in pictures and about $300 of it shopping - including a nice watch, plus another $150 on excursions, the rest was alcohol)