Final answer:
The death certificate is the essential document that must accompany remains during interstate transportation, often along with a burial transit permit or funerary shipping document based on state laws and transportation methods.
Step-by-step explanation:
When remains are being transported interstate, the death certificate is the primary document that must accompany them. This legal document serves as a vital record showing the date, place, and cause of death, and is essential for legal and administrative purposes. It confirms the legality of the remains' transportation and the identity of the deceased. In some cases, depending on the state laws and the means of transport, a burial transit permit or a funerary shipping document may also be required. These documents help ensure that the remains are handled with respect and in accordance with legal standards. They also facilitate the passage of the remains through any checkpoints or border crossings between states, and are often required by transportation companies like airlines.