Reading a parts invoice somebody else wrote
Start with the shape of the number
Manufacturer numbers follow house formats. An LR prefix and six digits is Land Rover. Two blocks of five is Toyota or Nissan. Eleven digits opening with a model series is Porsche. A letter then three groups is Mercedes.
A number that fits none of those shapes is usually aftermarket, and that is the first thing the invoice will not tell you. Our free OEM number lookup checks a number against the house formats without you memorising them.
Check whether it is still current
A genuine number can still be the wrong one to have fitted, if it was superseded before the job. Running it through the catalog shows whether it sits at the end of its chain or somewhere in the middle.
A middle link means the customer received the design the manufacturer had already moved away from. That is not automatically a fault, and it is worth knowing before you judge the repair.
Match the number against the actual car
A number can be genuine, current, and still belong to a different variant of the same model. This is where most quiet mistakes live, because the part fits well enough to be installed and then behaves oddly.
Resolve the customer’s VIN and compare. If the catalog specifies something else for that car, you have found your answer.
Labour lines and what they imply
Labour descriptions often reveal what was actually done more clearly than the parts lines. A part replaced without the fasteners and seals that normally accompany it suggests a repair done in a hurry.
The exploded diagram shows what should have gone with it. Our post on reading an exploded diagram covers how to read fitted quantities.
Frequently asked questions
How do I tell if a number on an invoice is genuine?
Check it against the manufacturer house format. Numbers that fit no known format are usually aftermarket.
What does it mean if the number is superseded?
The customer received a design the manufacturer has since replaced. It may still be serviceable, but it is not what ships today.
Can a genuine part still be wrong?
Yes. It can be genuine and current and belong to a different variant. Compare it against the car’s own VIN.