Massachusetts Auto Repair Rules (940 CMR 5.05) for Mobile Mechanics: the $10 Rule, Off-Premises Work, and What Goes on the Bill
Updated 2026-10-17. Sources are listed at the end.
Massachusetts regulates auto repair through the Attorney General’s consumer protection regulations. 940 CMR 5.05 lists what counts as an “unfair or deceptive act or practice” for a repair shop (940 CMR 5.05; official 940 CMR 5.00, Mass.gov). Several of its rules affect mobile work directly, and one exception was written with off-site repairs in mind.
Before work: record the basics
Before starting repairs, write down: the customer’s name, address and phone; the date and approximate time you received the vehicle; year, make and registration number; the odometer reading; and the specific repairs requested, or a short description of the problem (5.05(2)).
Authorization, the waiver, and the off-premises exception
Normally you can’t charge for repairs unless you have one of these (5.05(3)):
- written authorization signed by the customer listing the repairs and the total price (parts and labor)
- signed authorization listing the repairs, with charges posted on your premises
- if the repairs aren’t known up front, notice of the repairs and total price, and the customer’s authorization, before you start
- a signed waiver in the regulation’s wording, which lets you skip approval up to a dollar amount the customer writes in. It needs its own signature, separate from any other signature on the order
The off-premises exception: 5.05(3) “shall not be applicable if… at the customer’s request, repair services are rendered off the premises of the repair shop” (5.05(3)(e)). Read literally, that covers mobile work. It only lifts subsection (3). The rest of 5.05 still applies, including the $10 rule, the oral authorization records, and the bill. Most mobile techs get written approval anyway, because it’s the best defense in a payment dispute. See customer won’t pay?
Tell the customer before they authorize
Before getting authorization, tell the customer (5.05(4)):
- any storage charges and when they apply
- that they can have replaced parts back, or inspect them if the parts must go back under warranty or core return
- the amount of any estimate or diagnosis charge
A shop can meet this by posting the information on its premises. Mobile techs have nothing to post on, so put it in writing on the estimate, or say it at booking and in your confirmation text. Include your trip fee and diagnostic fee.
The $10 rule
If you find the vehicle needs other repairs, or the price will exceed the authorized price (or your posted price) by more than $10.00, you must tell the customer and get authorization before continuing (5.05(7)). Ten dollars is a small margin. A seized bolt that needs a new nut and an extra half hour usually goes over it.
Record every oral authorization
For any oral approval (new repairs, a higher price, more time), keep a written record of the date and time, who received it and who gave it, the exact authorization, and, if you placed the call, the number called (5.05(5)). A text thread helps, but copy the details onto the work order.
Timing, quality and conduct
- Same day: finish on the day the vehicle is delivered, unless the customer agrees to a delay or it was caused by something you couldn’t reasonably have anticipated (5.05(6)). If a part is back-ordered, get the customer’s OK to the new timeline.
- Fix poor work free: repairs not done “in a good and workmanlike manner in accordance with accepted trade standards” must be remedied promptly, at no charge (5.05(8)). Plan comebacks into your warranty policy.
- Don’t claim repairs are needed or done, or that a car is dangerous, when that’s not true (5.05(1)). Don’t charge for work you didn’t do, and don’t use the car for anything beyond a test drive without written permission (5.05(10), (12)).
What the bill must show
A dated written bill for every job, warranty work included (5.05(9)):
- customer and shop names and addresses, the date the vehicle was delivered, year, make, registration number and odometer reading
- an itemized list of repairs
- each part by name and number with its price, and total parts. Mark parts used, reconditioned or rebuilt if not new
- labor hours, whether they’re actual or flat-rate hours, the hourly price, and total labor
- the total
Posted flat-rate prices don’t need the parts and hours breakdown. Give the customer a copy of anything they sign (5.05(11)).
Sources
- 940 CMR 5.05, Repairs and services (via Cornell LII): https://www.law.cornell.edu/regulations/massachusetts/940-CMR-5-05
- Mass.gov, 940 CMR 5.00: Motor vehicle regulations: https://www.mass.gov/regulations/940-CMR-500-motor-vehicle-regulations