Whether you can use Onboard Credit (OBC) for gratuities depends on the specific type of credit you have and the cruise line's policy. Generally, "non-refundable" or "promotional" onboard credit—often given as a booking incentive—can be used for almost anything on the ship, including the daily service charges (gratuities) that are added to your stateroom account. Major lines like Royal Caribbean, Celebrity, and Carnival typically allow this, as the gratuities are simply another line item on your final folio. However, some lines, such as Princess Cruises, may restrict certain "Future Cruise Credits" (FCC) specifically to the cruise fare itself, meaning they cannot be applied to onboard spending or crew incentives. It is also worth noting that if you have "refundable" credit (money you overpaid or a gift from a travel agent), it will always cover gratuities first before being refunded to you at the end of the voyage. If your credit is labeled specifically as "Shop Credit" or "Spa Credit," it may be restricted to those specific departments. Always check your account via the cruise line's app on day one to see how your balance is being applied, and if in doubt, visit the Guest Services desk to confirm if your specific promotional credit will offset the mandatory daily tips.