How CARFAX Gets Its Information
The Short Answer
CARFAX does not inspect cars or investigate their pasts directly. It collects records that other organizations create during a vehicle's life, such as title transactions, service visits, accident reports and auction listings. It then matches those records to a specific car using the 17-character vehicle identification number (VIN). The qualification that matters most is this: a report can only show events that a participating source recorded and shared. If an event was never reported, it will not appear, so a clean report does not prove a clean history.
Where the Records Come From
CARFAX says its data comes from a large network of public and private sources across the US and Canada. The main types of contributor are listed below. Which specific organizations take part, and how complete their reporting is, varies by state, by business and over time.
State motor vehicle agencies: title issuance, registration renewals, ownership transfers, odometer readings recorded at title events, and title brands such as salvage, rebuilt, flood or lemon-law buyback. Police and fire departments: accident and incident reports that identify the vehicle involved. Insurance companies: claims and total-loss information, where it is shared. Collision repair shops: records of body and structural repair work. Service and maintenance facilities: dealer service departments, quick-lube chains and repair shops that report routine maintenance and repairs. Auto auctions: wholesale sales, often with condition notes or damage announcements. Dealerships: retail sales, trade-ins and reconditioning records. Rental and fleet companies: records showing a vehicle's prior commercial or rental use. Vehicle manufacturers: recall notices and some warranty-related data. State inspection stations: emissions and safety inspection results, including odometer readings in states that require inspections.
How the VIN Ties It Together
Each record that reaches CARFAX includes a VIN. The VIN is the common key that lets records from unrelated organizations be linked to the same car. CARFAX arranges those matched records in time order to build the report: when the car was titled, where it was registered, when it was serviced, what mileage readings were taken, and whether any damage or title brand was reported. Records tied to the VIN can include odometer readings from different points in time, and comparing them is one way to spot a possible mileage problem, such as a reading lower than an earlier one.
What the Report Can Miss
The report is only as complete as its sources, so some kinds of history are easy to miss.
Accidents settled privately or paid for out of pocket, with no police report or insurance claim. Repairs done at shops that do not share data with CARFAX, or work done by owners themselves. Events that were reported late, so a recent incident may not appear yet. Data entry errors at the source, such as a mistyped VIN or odometer reading, which can attach a record to the wrong car or create a false discrepancy. Details about how severe the damage was or how well it was repaired. A record may show that something happened without describing its extent.
How to Use the Information
Treat a CARFAX report as one input to a used-car decision, not a final verdict. Check that the VIN on the report matches the VIN on the car's dashboard, door jamb and title. Ask the seller for any service records of their own. Have an independent mechanic inspect the car before you buy. For open recalls, you can also check the VIN directly with the manufacturer or with the National Highway Traffic Safety Administration's recall lookup. Title-brand information is also available through approved providers of the National Motor Vehicle Title Information System (NMVTIS), the federal title database. Cross-checking that data can help confirm what a single report shows.
Note on scope: this guide does not give figures for how many sources or records CARFAX uses, because no confirmed numbers were available. Those totals also change over time.