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USDOT number decal requirements: what your truck must show

If your work truck needs a USDOT number, federal rules say what the marking on the truck must show and how it must read. The rule is short. It sets no letter height. It sets a distance test.

This guide covers who the rule applies to, what the marking says, where it goes on a wrap, and how to test it. It quotes the federal text from eCFR. It is not legal advice. Check FMCSA and your state DOT for your own trucks. To place the marking on a layout, use the free box truck wrap design tool and type it in the license line.

Who needs the marking

The marking rule, 49 CFR 390.21, applies to "every self-propelled CMV" under the federal safety rules (>eCFR 390.21). A commercial motor vehicle (CMV), per 49 CFR 390.5, is a vehicle used on a highway in interstate commerce that does one of these (>eCFR 390.5):

1. Has a gross vehicle weight rating or gross combination weight rating of 10,001 pounds or more.
2. Is designed or used to carry more than 8 passengers, driver included, for pay.
3. Is designed or used to carry more than 15 passengers, driver included, not for pay.
4. Hauls hazardous material in an amount that needs placards.

For a trades fleet, the first test matters most. A heavy pickup towing a loaded trailer can cross 10,001 pounds on its combination rating. Many box trucks are rated above it on their own. Look at the weight rating label on the driver door jamb.

"Interstate" covers trips across state lines. Some states require a USDOT number for trucks that stay inside the state. FMCSA keeps a list of those states on its >USDOT number page. Check it before you decide you are exempt.

What the marking must say

Rule 390.21(b) says the marking must show:

• The name. "The legal name or a single trade name of the motor carrier operating the self-propelled CMV," as it appears on your FMCSA registration.
• The number. "The identification number issued by FMCSA to the motor carrier," preceded by the letters "USDOT."
• "Operated by," when needed. If another company's name appears on the truck, your name and number must follow the words "operated by."

Other information can go on the truck "if it is not inconsistent" with the required lines. Your logo, phone, and services are fine.

A plain example: Brightvale Heating and Cooling, USDOT 1234567 (a fictional company and number).

Use the same name you filed with FMCSA. If your wrap says "Brightvale HVAC" but your filing says "Brightvale Heating and Cooling LLC," put the filed name in the DOT line. The big brand name can stay above it.

How the marking must look

Rule 390.21(c) says the marking must:

1. "Appear on both sides of the self-propelled CMV."
2. Be in letters that "contrast sharply in color with the background."
3. Be "readily legible, during daylight hours, from a distance of 50 feet" while the vehicle is parked.
4. Be kept legible over time.

The rule names no font or inch size. The 50-foot test is the standard. Rule 390.21(d) says the marking may be painted on or may be "a removable device" if it meets the same test. A magnet or a cut-vinyl decal can work.

Where the DOT line goes on a wrap

• Lower door, both sides. The cab door is where inspectors look first. Put the name and USDOT line on the lower half of each cab door, clear of the handle.
• Solid background. Set the line on a flat block of one color. A photo or gradient behind it fails the contrast test.
• Dark on light or light on dark. White letters on a navy door. Black letters on a white door. Avoid red on blue or yellow on white.
• Keep it apart from the phone number. The phone is for customers. The DOT line is for inspectors. Give each its own space so neither competes.
• Plan for the 50-foot test. Print the DOT line at full size on paper. Tape it to the door. Walk 50 feet from the truck in daylight. If you cannot read every digit, make it bigger.

Trailers: the truck carries the number

Rule 390.21 covers self-propelled vehicles. A trailer is not self-propelled, so the truck that tows it carries the USDOT marking. Trailers have their own rule: 49 CFR 393.11(b) requires retroreflective sheeting or reflectors on each trailer 80 inches or wider with a GVWR over 10,000 pounds, built on or after December 1, 1993 (>eCFR 393.11). A trailer wrap must leave that tape uncovered. See trailer lettering ideas.

Rented trucks

Rule 390.21(e) has a separate path for trucks rented for 30 days or less. The truck can carry the rental company's name and USDOT number if the rental agreement lists your name, address, and USDOT number and you keep a copy in the cab. Read the rule text before you rely on it.

State license lines are a separate rule

The USDOT line is federal. Many states add their own rules for contractor license numbers on trucks. Texas, for one, requires HVAC contractors to show the license number and company name in letters two inches high or taller on both sides of each vehicle. See HVAC van wrap ideas for the state examples.

Put it on your layout

1. Open the free box truck wrap design tool.
2. Type your business name, phone, website, and tagline. Type your USDOT line in the license line field.
3. See 24 free watermarked previews: 6 styles on 3 vehicles plus a yard sign. No account. The previews render in your browser.
4. Pick a layout where the DOT line sits on a solid block. Take it to your wrap shop.

Clean files cost $9 for one concept or $29 for all 24. They are concept proofs. Your shop sizes the DOT line on the print file for your truck.

FAQ

What are the USDOT number decal requirements? Under 49 CFR 390.21, the marking must show your legal or trade name and "USDOT" followed by your number. It must be on both sides, in sharp contrast, and readable from 50 feet in daylight while parked.

What size does a USDOT number have to be? The federal rule sets no inch height. It requires the marking to be readable from 50 feet in daylight while the truck is parked. Test a full-size print from 50 feet.

Do I need a DOT number for my truck? Under federal rules, a truck used in interstate commerce with a weight rating of 10,001 pounds or more counts as a commercial motor vehicle. Some states require a USDOT number for trucks that stay in state. Check FMCSA and your state DOT.

Can I use a magnet for my DOT number? Rule 390.21(d) allows "a removable device" if it meets the same legibility rules. A magnet that reads from 50 feet and stays on can work.

Does my trailer need a DOT number on it? The federal marking rule covers self-propelled vehicles, so the towing truck carries it. Large trailers need reflective conspicuity tape under 49 CFR 393.11.

Checked 2026-10-18. Prices and policies change. Confirm on the source before you buy.

Sources

• https://www.ecfr.gov/current/title-49/subtitle-B/chapter-III/subchapter-B/part-390/subpart-B/section-390.21
• https://www.ecfr.gov/current/title-49/subtitle-B/chapter-III/subchapter-B/part-390/subpart-A/section-390.5
• https://www.ecfr.gov/current/title-49/subtitle-B/chapter-III/subchapter-B/part-393/subpart-B/section-393.11
• https://www.fmcsa.dot.gov/registration/do-i-need-usdot-number
• https://wrapmockup.com/boxtruck-wrap-design/

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