Federal Excise Tax on Trailers: Design and Use-Based Exemptions

The 12% federal excise tax on heavy trailers has two separate sets of exemptions: one based on what the trailer is designed to do, and one based on who buys it or how it will be used. Design-based exemptions cover articles like farm feed and fertilizer bodies, house trailers, concrete mixers, and purpose-built mobile machinery chassis. Use-based exemptions cover sales for further manufacture, resale, export, and sales to state and local governments and qualifying nonprofit educational organizations. The design exemptions attach to the article itself. The use-based exemptions require IRS registration and a signed exemption certificate before the sale closes, and they can be revoked retroactively if the buyer changes course.

Before working through the exemptions, one boundary matters: the tax only applies to trailer and semitrailer chassis and bodies suitable for use with a trailer whose gross vehicle weight exceeds 26,000 pounds.¹ Trailers at or below that weight are outside the tax entirely, so no exemption is needed. If your trailer sits under the threshold, stop there. The rest of this article addresses trailers that would otherwise be taxable.

A trailer also has to qualify as a “highway vehicle” to be taxable in the first place. A trailer specially designed to function only as an enclosed stationary shelter at an off-highway site (an office trailer at a construction yard, for example) is not treated as a highway vehicle and falls outside the tax without needing to invoke any exemption.²

Exemptions Based on What the Trailer Is

These exemptions look only at the article’s design. Nothing about the buyer or the intended use matters, and no certification from the buyer is required.

Feed, Seed, and Fertilizer Equipment

A body primarily designed to process, prepare, haul, spread, load, or unload feed, seed, or fertilizer to or on farms is exempt. Spreader bodies and feed hauling bodies are the common examples.³ Important detail: the exemption reaches only the body and its parts and accessories. The chassis the body is mounted on remains taxable.⁴

Mobile Machinery

A chassis qualifies as exempt mobile machinery only if it meets all three of the following requirements:

Machinery or equipment is permanently attached (welded, bolted, or riveted) to the chassis for a construction, manufacturing, mining, farming, timbering, or similar operation unrelated to highway transportation.
The chassis is specially designed to serve only as a mobile carriage and mount for that particular machinery.
Because of that special design, the chassis could not be used to transport any other load without substantial structural modification.³

All three prongs have to be satisfied. A flatbed trailer that happens to carry a generator isn’t mobile machinery just because a generator is bolted down. The chassis itself has to be purpose-built and genuinely incapable of hauling ordinary freight. This is where audits most often unwind a claimed exemption.

Other Design-Based Exemptions

Several additional article types are carved out by statute:

Any house trailer is fully exempt.
Bodies designed to be mounted on a truck or trailer chassis and used to process or prepare concrete are exempt.
Boxes, bins, and similar containers designed as trash receptacles, not designed for hauling freight other than trash, and not permanently mounted on a truck chassis or body are exempt.
Chassis or bodies designed for use both as highway vehicles and railroad cars qualify. Piggyback trailers do not count.
Idling reduction devices that provide heat, air conditioning, or electricity to a parked tractor without running the main engine are exempt.³

Exemptions Based on Who Buys or How the Trailer Is Used

The second set of exemptions turns on the buyer or the intended use rather than the article’s design. These are governed by a different section of the code and, unlike the design-based exemptions, they require both parties to be registered with the IRS and require the seller to hold an exemption certificate from the buyer.

Sale for Further Manufacture

A trailer chassis or body sold for use in further manufacturing, or for resale to someone who will use it in further manufacturing, is tax-free at that initial sale.⁵ A chassis manufacturer can sell to a body builder without triggering the tax; the body builder then owes the FET on the first retail sale of the finished trailer. The tax isn’t eliminated. It’s deferred to whoever makes the first retail sale to an end user.

Sale for Resale

A dealer that buys a trailer for resale rather than for its own use owes no FET on that purchase. The dealer collects and remits the tax when the trailer is sold to the final customer.⁵

Export

Sales for export outside the United States are exempt, including sales to a buyer who will resell the article to a second purchaser for export. The article has to be exported before any domestic use occurs.⁵

The seller carries the risk. If the manufacturer doesn’t receive proof of export (or proof of resale for further manufacture) within six months of the sale date or the shipment date, whichever is earlier, the exemption disappears. The manufacturer then owes the full 12% tax as if the trailer had been sold at retail on the day the six-month window closed.⁶

State and Local Governments

Sales to a state, the District of Columbia, or any political subdivision for the government’s exclusive use are exempt. The purchase must be made directly by the governmental unit. A sale to a private contractor performing government work does not qualify, even if the government reimburses the contractor for the trailer.⁵

Nonprofit Educational Organizations

A nonprofit educational organization can purchase a trailer tax-free for its exclusive use. To qualify, the organization has to maintain a regular faculty and curriculum, have a regularly enrolled student body attending classes at its facilities, and be tax-exempt under IRC 501(a).⁷

Both the government and nonprofit educational organization exemptions are scheduled to expire for the FET on trailers and trucks on October 1, 2028. Until that date they remain fully available.⁵

What It Takes to Claim a Use-Based Exemption

An eligible buyer and an eligible use aren’t enough on their own. To sell tax-free under any of the exemptions in the previous section, the seller and buyer both have to be registered with the IRS, and the seller has to hold a valid exemption certificate before or at the time of sale.

Registration is done on Form 637, Application for Registration (For Certain Excise Tax Activities).⁸ Without registration, tax-free sales cannot be made, even where the underlying exemption clearly applies.⁹ The IRS assigns a registration number, and that number has to appear on exemption certificates for tax-free transactions.

The exemption certificate itself has to include the buyer’s name and address, the statutory basis for the exemption, and an acknowledgment that the buyer understands the tax consequences if the trailer is later used in a way that violates the exemption’s terms. A seller who accepts a good-faith certificate is generally relieved of liability if the buyer later violates the terms; at that point the buyer bears the tax.⁵ A seller who never collects the certificate has no such protection and stays on the hook for the full 12%.

Keep the certificates, the Form 637 registration letter, and all supporting records for at least three years after the date the tax became due or was paid, whichever is later.¹⁰ During an audit, the burden falls on the seller to produce a valid certificate for every sale treated as tax-free.

When an Exemption Is Lost

A use-based exemption isn’t permanent. If you buy a trailer tax-free and then put it to a different purpose, you become liable for the 12% tax yourself. The IRS treats the change in use as if you had made a retail sale to yourself, and the tax is figured on the price at which similar trailers sell at retail in the ordinary course of trade, not on what you originally paid.¹¹

The same rule catches trailers bought tax-free for resale. If you start using one in your own operations instead of selling it, you owe the tax as if you had manufactured the trailer and made the first retail sale. The liability is reported on Form 720 for the quarter in which the use change occurred.

Rebuilt Trailers and the 75% Rule

Used trailers normally escape the FET because the tax applies only to the first retail sale. Extensive rebuilding can bring the tax back. If the cost of repairs and modifications exceeds 75% of the retail price of a comparable new trailer, the IRS treats the rebuilt trailer as a new taxable article.¹² The rule covers modifications that change what the trailer does or restore a wrecked trailer to working condition. Spend $85,000 refurbishing a trailer when a comparable new one retails for $110,000, and you have crossed the line. One limit worth noting: the rule generally does not apply to a trailer that was not subject to the tax when it was originally new.

Penalties for a Wrongly Claimed Exemption

Claiming an exemption you can’t back up costs more than just the underlying tax. If you fail to file Form 720 by the deadline, the penalty is 5% of the unpaid tax for each month or partial month the return is late, up to 25%.¹³ Filing on time but not paying triggers a separate 0.5% monthly penalty on the unpaid balance, also capped at 25%.¹⁴

If the IRS determines that an underpayment resulted from negligence or disregard of the rules, an additional accuracy-related penalty of 20% of the underpayment applies on top of everything else.¹⁵ Claiming an exemption without proper documentation, or applying the wrong weight threshold, are exactly the kinds of errors the IRS characterizes as negligence. On a $150,000 trailer, the base tax alone is $18,000, and adding a year of late penalties plus the accuracy penalty pushes the total close to $30,000.

1
Office of the Law Revision Counsel. 26 U.S. Code 4051 – Imposition of Tax on Heavy Trucks and Trailers
2
Internal Revenue Service. Publication 510 (12/2025), Excise Taxes – Section: Nontransportation Trailers and Semitrailers
3
Office of the Law Revision Counsel. 26 U.S. Code 4053 – Exemptions
4
Internal Revenue Service. Publication 510 (12/2025), Excise Taxes – Section: Farm Feed, Seed, and Fertilizer Equipment
5
Office of the Law Revision Counsel. 26 U.S. Code 4221 – Certain Tax-Free Sales
6
eCFR. 26 CFR 48.4221-3 – Tax-Free Sale of Articles for Export
7
Internal Revenue Service. Publication 510 (12/2025), Excise Taxes – Section: Nonprofit Educational Organization
8
Internal Revenue Service. 637 Registration Program
9
eCFR. 26 CFR 48.4222(a)-1 – Registration
10
Internal Revenue Service. How Long Should I Keep Records?
11
Internal Revenue Service. Publication 510 (12/2025), Excise Taxes – Section: Use Treated as Sale
12
Internal Revenue Service. Publication 510 (12/2025), Excise Taxes – Section: Retail Tax on Heavy Trucks, Trailers, and Tractors
13
Office of the Law Revision Counsel. 26 U.S. Code 6651 – Failure to File Tax Return or to Pay Tax
14
Internal Revenue Service. Failure to Pay Penalty
15
Office of the Law Revision Counsel. 26 U.S. Code 6662 – Imposition of Accuracy-Related Penalty on Underpayments