Customs forms are required for packages sent to FPO addresses, according to the U.S. Post Office. The specific form needed depends on the shipping service and the declared value of the contents.
Mail to FPO addresses is subject to more restrictions than most U.S. mail. The recipient's full name must be included with the address. The unit and zip code, if there is one assigned, must be shown, and a return address is required.
No obscene or pornographic material is allowed to FPO locations. Political or religious materials, as well as pork products, are generally not allowed. The contents may be further limited by the regulations of the country where the base is located. The U.S. Post Office website can help shippers figure out which customs regulations and forms apply.