Form DR 2173 at a glance
What it is: Bill of Sale for Motor Vehicle.
Who signs: Sign the Seller/Seller's Agent signature line and enter the date. Buyer's signature (1) is required, and Buyer's signature (2) is required.
A filled-in Form DR 2173 example: a seller sells a car to two buyers

How to fill out Form DR 2173, box by box
Vehicle Identification Number and Date of Sale

For and in consideration of $ you enter, the undersigned Seller grants, sells, transfers, and conveys to the Buyer, and to Buyer's heirs, personal representatives and assigns, the following motor vehicle.
Enter the Vehicle Identification Number (VIN), Year, Make, Body, Model and Date of Sale.
The undersigned Seller covenants with the Buyer that the undersigned Seller is the lawful owner of the motor vehicle; that the undersigned Seller has good right to sell the same and will warrant and defend the same against the lawful claims and demands of all persons.
This motor vehicle and equipment is sold and accepted as is.
Current Odometer Reading

Federal law requires that you state the odometer mileage upon transfer of ownership, failure to complete or providing a false statement may result in fines and/or imprisonment.
Enter the Current Odometer Reading (No Tenths of Miles). To the best of my knowledge: the odometer reading is the actual mileage of the vehicle, or the odometer reading is in excess of its mechanical limits, or the odometer reading is not the actual mileage, which is a warning odometer discrepancy.
Seller Signature and Address

Seller(s) certify under penalty of perjury that the statement is true and correct to the best of their knowledge. Buyer's signature acknowledges transfer of ownership and receipt of odometer statement.
Enter the Seller/Selling Company/Agency (Please Print) and the Seller/Seller's Agent handprinted name.
Enter the Seller's street address, city, state and zip.
Sources
[1] Form DR 2173, Bill of Sale for Motor Vehicle (the served file; no issuer file found) (the Official source link on this page).

