The Dolly Needs Its Own Annual Inspection
The rule counts each unit of a combination on its own. And the inspection paperwork has to ride on the vehicle itself.

Ask most operators when their annual inspection is due and you get one date. The rule does not work that way.
49 CFR 396.17 opens by defining what it is inspecting, and the definition is the part that costs people money: the term commercial motor vehicle includes each vehicle in a combination vehicle.
The regulation spells out its own example. For a tractor, semitrailer and full trailer combination, the tractor, the semitrailer and the full trailer must each be inspected, including the converter dolly if so equipped.
The dolly is a vehicle
That last clause is the one that gets skipped. A converter dolly has no cab, no engine and no VIN plate anybody looks at, and it spends most of its life parked against a fence. Under this section it is a vehicle, and it needs its own inspection like everything else rolling.
The same logic covers the trailer that only comes out in season, the spare that lives in the back row and the unit you borrowed from a friend last week. Anything in the combination counts.
What twelve months actually means
Paragraph (c) is the operative sentence. A carrier must not use a commercial motor vehicle unless each component identified in appendix A has passed an inspection at least once during the preceding 12 months, and documentation of that inspection is on the vehicle.
Two halves, and the second is the one that fails at the scale. The inspection can be perfect and a year fresh, and if the paper is in a filing cabinet at the shop, the truck does not meet the requirement while it is rolling.
The documentation can be the inspection report itself under 396.21(a), or something based on it, such as a sticker or decal. If it is a decal, paragraph (c)(2) says it has to carry four things:
1. The date of inspection.
2. The name and address of the carrier, intermodal equipment provider or other entity where the inspection report is kept.
3. Information uniquely identifying the vehicle, if it is not clearly marked on the vehicle itself.
4. A certification that the vehicle passed an inspection under 396.17.
A blank sticker with a punched month is not that. A decal that names a shop that closed two years ago is not that either, because item two is where the report lives.
Who is allowed to sign it
Paragraph (d) lets a carrier perform its own annual inspection on vehicles under its control. Paragraph (e) lets it use a commercial garage, fleet leasing company, truck stop or similar business as its agent, provided that business has facilities appropriate for the work and employs qualified inspectors.
Qualified is defined, not assumed. Section 396.19 says the individual has to understand the criteria in part 393 and appendix A, has to have mastered the methods and tools, and has to be capable by reason of experience, training or both. That last one resolves to either a completed federal or state training program, or a certificate from a state or Canadian province, or a combination of training and experience totaling at least one year.
And then the part carriers forget: under 396.19(b), the carrier has to retain evidence of that person's qualifications for as long as they are doing its annual inspections, and for one year after. If your annual inspections are done in house, that file is part of the requirement, not a nicety.
The month-end detail worth knowing
Paragraph (f) handles vehicles that pass a periodic inspection run by a state, by a Canadian province or the Yukon Territory, or by Mexico, where that program meets the appendix A minimums. Those count as meeting the annual requirement.
For how long is the useful part: 12 months commencing from the last day of the month in which the inspection was performed.
Not twelve months from the day it was done. From the end of that month. An inspection on the third of March and one on the thirty-first of March expire on the same date, which is a few free days if you know about them and a surprise if you do not.
How to audit this in one pass
Walk the yard with a list of every unit you own or control, dollies included. For each one, answer three questions in order:
Is it within twelve months? If you cannot answer from the unit itself, that is already the second problem.
Is the documentation on it? Not in the office. On it.
Does the decal carry all four items? Read 396.17(c)(2) once with a decal in front of you; it is a short list and it is easy to come up one item short.
The units that fail are almost never the tractors. They are the trailer that sat out a season, the dolly, and the piece of equipment that came in on a trade and never got entered into anybody's schedule.
Time it with the work you were doing anyway
The cheapest annual inspection is the one that happens while the unit is already in the shop for brakes, suspension or tires. The components overlap, the truck is already down, and a defect found then is a repair instead of a shutdown.
We do annual inspections and the repairs that come out of them in Houston, Dallas and Monterrey: thetrucksavers.com.
Source: Electronic Code of Federal Regulations, 49 CFR 396.17, Periodic inspection