A hazmat declaration is the answer you give, at the moment you buy the label, to one question: does this package contain hazardous material? On a USPS label that answer changes the code inside the barcode, which services you may use, which box you may use and how you hand the package over. USPS makes the mailer responsible for answering.

This post follows one ordinary sale, a used phone, through each of those changes. For the list of what counts as hazmat, read Can You Ship That?; for the fee and the carrier-by-carrier rules, the main site keeps the HAZMAT shipping guide current.

Who has to declare, and when

USPS Publication 52, section 323.1 puts it plainly: “Full responsibility rests with the mailer to comply with all Postal Service and non-Postal Service laws and regulations.” The same section says mailers “must identify whether a shipment contains hazardous materials when generating the label.”

Two consequences follow for a seller who prints labels at home:

  • The declaration happens when the label is created, on the screen, before you pay. There is no later form to fill in.
  • The label software cannot declare for you. It can only ask. If you say nothing, the label is issued as an ordinary package and the responsibility stays with you.

The worked example: a used phone

You sold a two-year-old phone. It works, the battery is installed, and it is not in the manufacturer’s sealed box.

Step 1: classify the phone

Publication 52 treats a device as “used, damaged, or defective” unless it is new in original packaging or is a manufacturer-certified new or refurbished device (section 349). Your phone is used. Under section 327, used, damaged or defective electronic devices containing or packaged with lithium batteries are prohibited from air transportation, and section 349 also bars them from international mail.

So the answer to the question is yes, and the package has to travel by surface.

Step 2: declare the phone on the label

In I’d Ship That the declaration lives on the “Confirm Details” screen, in a row labelled “Hazmat Declaration”. Tapping it opens a picker, “Select a Hazmat Type”, with entries such as “Class 9 - New lithium battery package with device”, “Class 3 - Package containing flammable liquids” and “Ground transport only package”. If you do not know which entry fits, the “Lookup HAZMAT Code” helper asks what you are shipping and suggests one. Changing the declaration re-prices the shipment, because the answer changes which services are valid.

Whatever software you use, the step looks similar: a question, a category, then rates.

Step 3: what the declaration changes on the label

A USPS barcode carries a three-digit Service Type Code that tells sorting equipment what the package is. Publication 52 section 323.2 requires a unique Service Type Code for each package containing hazardous materials, and section 323.4 requires the label provider to send USPS an electronic record carrying that code before or with the shipment.

In practice the declaration is what lets the network keep your phone off an aircraft. An undeclared phone carries an ordinary code, and nothing in the barcode tells the equipment to route it by surface.

Step 4: what the declaration changes about the service

Hazardous materials sent by Priority Mail Express or Priority Mail must be eligible for air transportation (Publication 52, section 327). A used phone is not. The service left is USPS Ground Advantage.

The fee table favors the compliant choice. Notice 123, the USPS price list effective October 4, 2026, lists the HAZMAT handling fee as $0.00 on USPS Ground Advantage and $7.50 on Priority Mail and Priority Mail Express. Current postage for the service itself is on the USPS Ground Advantage rates page.

Step 5: what the declaration changes about the box

Publication 52 section 349.221 sets the packaging rules for every mailable lithium battery, this phone included, and USPS adds two of its own:

  • No free USPS packaging. USPS states that restricted hazardous materials cannot ship in free Priority Mail packaging. The app enforces the same rule: with a hazmat type selected, USPS flat rate boxes and envelopes show as “Incompatible with hazmat”. Use your own box.
  • A rigid outer box. Section 349.221 requires rigid outer packaging. Section 339.4 allows a padded or poly bag only when every one of its conditions is met: the device is new or manufacturer refurbished, it sits in secondary packaging such as the manufacturer’s box that can withstand a 1.2 meter drop test, the device gives the battery adequate protection, and the outer packaging neither shows nor is required to show hazardous text, markings or labels. A used phone fails the first condition, so it needs the rigid box. For a package of 20 pounds or less, the same section calls for a box rated at a 200 lb burst test or 32 edge crush test, or equivalent.
  • A phone that cannot switch on in transit. Equipment containing lithium batteries “must have effective means of preventing it from being inadvertently turned on or activated,” and a battery installed in equipment “must be protected from damage and short circuit.” Power the phone off, and pack it so nothing presses on a button.
  • Cushioning that holds it still. The device must be “individually cushioned, creating separation to prevent movement or damage.” A phone that can slide inside the box does not meet that.
  • Two lines of text on the address side. Publication 52 section 349.221 requires a package holding a used, damaged or defective device to be marked “Restricted Electronic Device” and “Surface Transportation Only” on the address side.
  • A clean box. If you reuse a box, USPS says to make sure “all old logos, barcodes, shipping labels, and addresses are covered or blacked out”. An old battery mark or hazard diamond left on a reused box describes contents that are not there.

Step 6: what the declaration changes at hand-off

USPS’s shipping restrictions page says you “must separate HAZMAT packages from all other packages and present them in a container marked ‘HAZMAT.’” For a home seller with one phone and five ordinary parcels, that means the phone does not go in the same tote as the rest.

One more effect to plan around: USPS Package Intercept, the service for recalling a package after it ships, excludes items marked for surface-only transport and hazardous materials. If the buyer gave the wrong address, a declared surface-only package cannot be redirected that way, so check the address before it leaves.

The same six steps for a bottle of perfume

Perfume containing alcohol is a flammable liquid. Publication 52 section 343 prohibits flammable liquids in domestic air mail and international mail, and allows them by domestic surface when they qualify as a Limited Quantity surface material. The USPS shipping restrictions page says the same thing in one sentence: perfume containing alcohol “may be shipped within the United States by ground transportation.”

Step Used phone Perfume containing alcohol
Declare when buying the label Yes Yes
Service USPS Ground Advantage USPS Ground Advantage
International Not allowed Not allowed
Marking on the address side “Restricted Electronic Device” and “Surface Transportation Only” DOT Limited Quantity surface marking (section 343.3)
Packaging Your own rigid box; device unable to switch on and cushioned so it cannot move (section 349.221) Your own box, packed to Packaging Instruction 3A at any bottle size: a securely closed bottle, cushioning around it that prevents breakage and absorbs any leak, securely sealed secondary packaging, and a strong outer box
Present separately from other mail Yes Yes

Section 343.21 says mailable flammable liquids “must be prepared according to Packaging Instruction 3A,” and that instruction has no small-bottle exception. The 4 fluid ounce threshold for triple packaging in the general liquid rules is not the test here. What Packaging Instruction 3A requires:

  • A flashpoint above 20°F. A flammable liquid with a flashpoint of 20°F or below is not mailable at all. The manufacturer can tell you the flashpoint of your product.
  • A quantity limit set by the flashpoint. With a flashpoint above 20°F and not more than 73°F, a nonmetal bottle may hold no more than 1 pint, and that is also the total per package. Above 73°F and below 100°F, the limit is 1 quart.
  • A secure closure. A screw cap with at least one and a half turns, or another means of secure closure. Friction tops are not acceptable.
  • Three layers. Enough cushioning around the bottle “to prevent breakage and absorb any potential leakage,” packed with the bottle in securely sealed secondary packaging, inside a strong outer box that holds both firmly.

The general liquid rules still apply on top: DMM 601.3.4 requires the outer box to be marked to show it holds liquid, and a package holding more than 4 ounces of liquid needs orientation arrows on two opposite sides (section 223). Look your product up in the USPS HAZMAT search tool before you list it.

The mistake, and the fix

The common mistake is not shipping something forbidden. The common mistake is buying a Priority Mail label for a used phone because it is faster, and leaving the hazmat question blank because the phone “is just a phone”.

That single choice breaks three rules at once: the device is undeclared, it is on an air service it may not use, and the box lacks the required marking. USPS lists a $50.00 HAZMAT noncompliance fee for commercial shipments that are improperly declared, and separately a civil penalty of at least $250 and up to $100,000 for knowingly mailing dangerous material.

If the label is already bought but the package has not been handed over, the fix is simple. Cancel the label, create a new one with the declaration, choose USPS Ground Advantage, and mark the box. Once the package is in the mail the choices narrow, which is the best argument for answering the question correctly the first time.

A pre-label checklist for anything with a battery, a spray nozzle or a scent

  1. Is the item new in sealed manufacturer packaging, or used? Used electronics go by surface.
  2. Does it contain alcohol, a propellant or a flammable solvent? Look it up in the USPS HAZMAT search tool.
  3. Select the hazmat category before requesting rates, so the services offered are the valid ones.
  4. Use your own box, and strip or cover every old marking.
  5. Pack to the rule for the item. A device with a lithium battery goes in a rigid box, unable to switch on, cushioned so it cannot move. A flammable liquid gets absorbent cushioning, sealed secondary packaging and a strong outer box, whatever the bottle size.
  6. Add the required marking on the address side.
  7. Keep the package apart from your ordinary parcels when you hand it over.

Sources

Checked October 12, 2026 against USPS Publication 52 sections 323, 327, 329, 339, 343 and 349, section 223 and Packaging Instruction 3A; Notice 123 (prices effective October 4, 2026); DMM 601; and the USPS pages on shipping restrictions, preparing packages and Package Intercept. App screen text was read from the I’d Ship That source code the same day. This post covers USPS domestic mail only; UPS has its own hazardous materials program and rules.