Onboard credit is money credited to your cruise account for you to spend while on the ship. It’s typically use-it-or-lose-it, so you need to spend it all before leaving the ship.
How Do You Get Onboard Credit?

There are many ways to get onboard credit. You can get onboard credit from the cruise line through a promotion or as compensation for an issue. Your travel agent can also gift you onboard credit. You can also get onboard credit by referring friends to cruise and being a cruise shareholder.
What Can You Spend It On?

You can spend your onboard credit on drinks, specialty dining restaurants, spa treatments, shore excursions, laundry service, and WiFi packages. You can also buy souvenirs and luxury goods at the cruise gift shop.
Can You Use Onboard Credit on Gratuities?

Whether or not you can use onboard credit to pay gratuities will depend on the cruise line. Some cruise lines like MSC Cruises and Celebrity Cruises will allow you to pay your gratuities with your onboard credit. While Norwegian Cruise does not let you use onboard credit to pay gratuities.
Can You Spend Your Onboard Credit Before Boarding the Ship?

Some cruise lines let you use onboard credit to buy cruise extras before boarding the ship. For example, Celebrity Cruises will let you book shore excursions and buy drink packages, specialty dining packages, WiFi, and even laundry service before boarding the ship. Other cruise lines won’t let you use your onboard credit until you are on the ship.
Can You Combine Onboard Credit from Various Sources?

When you check your onboard credit balance, it will be the total amount. The cruise line automatically combines all your onboard credit from different sources. For example, if you got $100 from the cruise line through a promotion and $50 from your travel agent, then your total onboard credit is $150. Check out Caribbean Cruise versus Alaska Cruise: Pros and Cons
What Happens If You Don’t Use All Your Onboard Credit?

Most onboard credits are “Use It or Lose It,” which means you won’t get a refund if you don’t use up all your onboard credit. Make sure to spend every penny of your onboard credit, or it will go to waste! Buy a souvenir or a cruise photo- make sure to use it up on the last day!
Do know that in some rare instances, your onboard credit can be refunded back to you after the cruise. If you are unsure, check with guest services, so you know what to expect. Check out 13 Easy Ways to Get Free Things on a Cruise- If you Ask
How Do You Check Your Onboard Credit Balance?

The easiest way to check your onboard credit balance is on your cruise app. You can also check your cruise TV for your balance. Otherwise, you can ask guest services for your balance but know there is usually a long line at the desk. Check out 8 Easy Ways to Get Free Onboard Credit on a Cruise
Can You Check Your Onboard Credit Balance Before Boarding the Ship?

Some cruise lines will let you check your onboard credit before boarding the ship. You can do this by logging into your booking on the cruise website. However, depending on the cruise line, your onboard total may be incomplete. For example, with Celebrity Cruise, you can only see the onboard credit from the cruise line, but the onboard credit gift from your travel agent will only appear in your account after you board the ship. Check out 30 Unusual Things to Pack for a Cruise: Things You Didn’t Know You Need
Can I Use Onboard Credit at the Cruise Terminal Shops?

You won’t be able to spend your onboard credit at the cruise terminal gift shops. That’s because the cruise terminal shops are independently owned and typically not affiliated with the cruise line. Check out What to Pack: Alaska cruise (free packing list)
What’s the Difference Between Onboard Credit and Future Cruise Credit?

Onboard credit and Future Cruise Credit are not the same thing. Onboard credit is money you can use on the ship during your cruise to buy drinks, shore excursions, dining, and WiFi, which typically expires at the end of your cruise. While Future Cruise Credit is money you can use to book a future cruise, you can’t use it while onboard the ship. Check out What to Pack: Caribbean cruise (free packing list)