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Lettering Your Truck: How the USDOT Number Has to Be Displayed

Updated September 2026

It is the cheapest rule to follow and one of the easiest to be written up for, because an officer can see it from the next lane. 49 CFR 390.21 is short; here is all of it that matters to a small fleet.

What it has to say

  1. Your legal name or a single trade name, exactly as it appears on your FMCSA registration (the MCS-150).
  2. Your number, preceded by the letters "USDOT" — USDOT 1234567, not just the digits.

If another name is on the vehicle as well — a lessor, a franchise brand — then the name of the carrier actually operating it has to appear too, preceded by the words "operated by" (390.21(b)).

How it has to look

Under 390.21(c), the marking must:

  • Appear on both sides of the self-propelled vehicle
  • Be in letters that contrast sharply with the background
  • Be readily legible, in daylight, from 50 feet while the vehicle is standing still
  • Be kept legible — faded or peeling lettering stops counting

The rule sets no letter height. Fifty feet is the test: plain, bold lettering in a colour that stands out from the paint passes it, and thin script close to the paint colour does not.

Are magnetic signs allowed?

Yes. The marking "may be painted on the CMV or may consist of a removable device" (390.21(d)), as long as it meets the same legibility requirements. Two cautions: a magnet that has blown off is no marking at all, and some states have their own lettering rules for in-state work that are stricter than this one.

Rented and borrowed trucks

A truck rented for 30 days or less can run under the rental company's markings, provided the rental agreement carried in the vehicle names you as the renter and shows your USDOT number (390.21(e)). Longer than that, it needs your name and number like any other truck you operate.

The name has to match

The most common mistake is not size — it is lettering that doesn't match the registration. If your MCS-150 says "J. Rivera Hauling LLC" and the door says "Rivera's Junk & Demo," update one or the other. A trade name is fine; it has to be the one on file.

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This is general information, not legal advice, and RelayPoint is not a law firm or a compliance consultant. Source: 49 CFR 390.21 (marking of self-propelled CMVs and intermodal equipment), as published in September 2026. States may have additional marking requirements for in-state operations, and for-hire carriers may have other identification requirements. Confirm your obligations with the FMCSA or your state's motor carrier authority.