Holiday shipping season is about to bury post offices in cardboard, and a surprising number of everyday things are not allowed inside any of it. The U.S. Postal Inspection Service, the law enforcement arm of the postal system, keeps a list of items that can never be mailed, and the penalties for ignoring it are steep.
Eight items on that list tend to catch people off guard: fireworks, live ammunition, explosives, gasoline, liquid mercury, air bags, large lithium batteries and marijuana. According to the Postal Inspection Service, mailing prohibited or restricted items can bring civil and criminal penalties, with fines that can top $150,000 for each violation.
Item 1: Fireworks, Sparklers Included
The calendar is what makes the list urgent, because boxes headed for Christmas delivery start moving in force soon. USPS has said Ground Advantage packages should ship by Dec. 17 to arrive in time. Anyone who would rather carry gifts than ship them can look at carry-on suitcases worth packing for Thanksgiving travel and skip the post office line entirely.
Fireworks of every kind are the headline offender. A 2025 USPS reminder lists sparklers, firecrackers, bottle rockets and Roman candles as strictly prohibited, classed as hazardous materials and barred from air and ground transportation alike. Acting Postmaster General Doug Tulino said that “even small items like firecrackers or bottle rockets can cause fires, explosions or injuries if mishandled.”
The same notice said the Postal Inspection Service opened 1,700 investigations in the previous year into customers trying to send hazardous materials, fireworks and explosives among them. Sparklers may feel like a harmless souvenir, and fireworks are part of the odd American traditions that puzzle visitors, but the mail is not a place for them.
Items 2 to 4: Ammunition, Explosives and Gasoline
Plenty of holiday mail carries no risk at all. A handwritten card, one of the little rituals from the 80s and 90s that faded without much notice, has no restrictions. Legal packages still face trouble at the other end, which is why the advice on what never to do with holiday packages left on the porch is worth a read. The banned items below never get that far.
Item 2: live ammunition. The Postal Inspection Service’s hazardous materials page says small arms ammunition, primers, blank cartridges and propellant powder for firearms are strictly prohibited from the mail. Because Priority Mail boxes already carry a holiday surcharge, a package turned away at the counter is a pricey mistake as well as a legal one.
Item 3: explosives. They sit on the same never-mailable list as ammunition, with no carve-out for small quantities. Households heading out of town for the holidays can run through 10 things to do before leaving the house empty instead, and pack with 3-piece luggage sets for holiday trips in mind.
Item 4: gasoline. Fuel is on the list too. A gas can is not a gift, and it is not a shipment either.
Items 5 to 7: Mercury, Air Bags and Big Batteries
Item 5: liquid mercury. The Postal Inspection Service says liquid mercury, on its own or contained in various items, is prohibited in the mail. The wording is broad on purpose, since the ban covers the metal even when it is inside something else.
Item 6: air bags. They are named among the strictly prohibited items on the same page, right alongside the more obvious hazards.
Item 7: large lithium batteries. Batteries that power e-bikes, scooters and generators are strictly prohibited from being mailed because they exceed the 100 watt-hour limit. Smaller lithium-ion batteries rated at 100 watt-hours or less can be mailed in limited quantities under USPS requirements, so the size on the label matters. A quick comparison of the printed rating with that 100 watt-hour line before heading to the counter settles most doubts, and anything over it needs another way to travel.
Item 8: Marijuana, and the Rulebook to Check First
Marijuana. It is named on the never-mailable list too, which makes holiday care packages a poor place to test the rule.
For anything borderline, the Postal Inspection Service points customers to Publication 52, Hazardous, Restricted, and Perishable Mail, before the box gets sealed. Checking takes a few minutes. Dealing with a returned package, a fine or an investigation takes a lot longer.
Every item above stays out of the box, and everything else follows the usual rules.
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This article was produced with AI assistance and edited for accuracy against the sources linked above.
Image: Elliott R. Plack – CC0/Wikimedia Commons
