You can ask the agency you booked through, but there’s no way to see it in your account until you are on board.
Because this gets asked so often I've compiled a list of things to spend OBC on. One thing I know of now that you CAN'T buy with OBC is a deposit on a Future Cruise. You need a credit card for that. Also, there may be some card game in the casino with a cash only buy-in. And if they do a fundraiser, like selling t-shirts to “save the reefs” and the like, expect to need cash for that. Otherwise, here you go:
*Acupuncture
*Airport transfers
*Alcove/cabana Rental (some ships)
*Apple products, go-pro, etc
*Art Auction Purchases
*Babysitting
*Barber Shop services
*Behind the Scenes Tours
*Beverages -- Alcoholic, carbonated soft drinks, specialty coffees and teas, bottled water — if not in your package, also beverages above your package limits
*Bingo and Deal or No Deal
*Bottles of wine
*Casino
*Chef’s Table
*Corkage charged if you bring your own bottles of wine to the MDR
*Duty free liquor and cigarettes
*Extra cost entrees and other items in Main Dining Room and specialty restaurants
*Extend Your Stay program
*Fitness classes
*Flowers
*Gelato
*Gift shop souvenirs, purses, watches, cosmetics, clothing, jewelry, etc.
*Gratuities, and extra gratuities
*Guests dining with you in Luminae (applies to Suite Passengers only)
*Guest entertainers' CD's and DVD's
*Hair and nail salon
*Hollywood hot glass experiences (some ships)
*Internet if not in your package, also Internet upcharges
*Laundry/pressing/drycleaning
*Liquor Tasting events
*Luggage Valet (FLL and MIA only)
*Martini Flights
*Medical Center purchases
*Mini bar
*Portrait photo sessions
*Pay-per-view movies
*Persian Gardens passes
*Personal Training Sessions
*Photos & cameras
*Room service fees
*Ryde spinning classes
*Shore Excursions
*Shuttle to town (some ports)
*Spa -- massages and treatments
*Specialty restaurants
*Teeth Whitening
*Telephone calls using ship's system
*Transfer to another passenger's account
*Voyage in Review DVD
*Wine and liquor tastings
*Zumba
They will always use non-refundable OBC first, then refundable OBC, And if you run out of that then it goes on your credit card