One carrier, not several
This is the fact families are most often surprised by. The major private parcel carriers do not accept cremated remains, so the choice is not which shipper costs least — it is USPS or hand-carry. Attempting to ship them by another carrier risks a package that is refused, or worse, mishandled as an ordinary parcel.
Service class and label
Domestically, cremated remains must go by Priority Mail Express. Internationally, Priority Mail Express International, and only to countries that permit it — the destination’s own import rules apply and some prohibit it outright. The outer packaging must display Label 139, the special marking that identifies the contents so the package is handled correctly at every stage.
The Post Office supplies a kit designed for this, which includes the label and appropriate packaging.
Packaging that actually survives
Use a sealed, siftproof inner container — the plastic container the crematory supplies is designed for this. Pad it inside a sturdy outer box so nothing shifts. Include a note inside with the sender and recipient details, so the package can be reunited with its addressee if the outer label is damaged.
Tracking and signature confirmation are worth having, and Priority Mail Express includes tracking as standard.
Documents to include
A copy of the death certificate and the certificate of cremation should travel with the package, particularly internationally where customs will want to know what is in the box. For international shipments, check the destination country’s consulate before posting.