Buying or selling a used car in Illinois comes with more paperwork than most people expect. Between the title, tax forms, and registration deadlines, it's easy to overlook one small document that can save you a lot of trouble later: the bill of sale.

Illinois doesn't require a state-issued bill of sale form to transfer a title, but that doesn't mean you should skip it. This guide breaks down exactly what an Illinois bill of sale is, when you need one, what it must include, and how it fits into the broader title and registration process — all based on current guidance from the Illinois Secretary of State (ILSOS) and the Illinois Department of Revenue (IDOR).

What Is an Illinois Bill of Sale?

A bill of sale is a written record of a vehicle transaction. It documents who sold the car, who bought it, what vehicle changed hands, and for how much. Think of it as a receipt with legal weight — it protects both the buyer and the seller if a dispute comes up later.

In Illinois, the bill of sale works alongside the title, not instead of it. The title is what legally transfers ownership. The bill of sale backs that up with proof of the sale price and the date of the transaction, which matters for tax purposes.

Is a Bill of Sale Required in Illinois?

This is where Illinois differs from many other states. Illinois does not strictly require a separate bill of sale to transfer a title if the purchase price is already listed on the title assignment itself, according to Secretary of State guidance (source: ILSOS, Apply for Registration and Title). So technically, a private sale can be completed without a standalone bill of sale document.

That said, having one is still worth the five minutes it takes to fill out. Here's why:

• It gives you a paper record of the exact purchase price, which matters when the buyer files the private-party use tax form

• It documents the odometer reading and sale date in one place

• It protects the seller if the buyer delays registering the car or transferring liability

• It's useful if either party needs to prove the transaction happened for insurance, legal, or tax reasons

The Illinois Department of Revenue actually leans on this document directly. When you buy a vehicle from an out-of-state dealer and bring it into Illinois, you're required to attach a copy of the bill of sale as proof of the purchase price when filing your tax form (source: IDOR, Illinois Tax Requirements for Vehicles). For private-party purchases within Illinois, attaching a copy of the bill of sale or proof of purchase to your RUT-50 tax form may prevent future notices from the state questioning your reported price (source: IDOR, Private Party Vehicle Use Tax).

What Should an Illinois Bill of Sale Include?

There's no official state-issued template, so you or the buyer can draft one — but it should cover the same core details every time. A complete bill of sale typically includes:

• Full names, addresses, and contact information for both buyer and seller

• Vehicle year, make, model, color, and Vehicle Identification Number (VIN)

• Odometer reading at the time of sale

• Sale date

• Purchase price (or a note that the vehicle was a gift)

• Any liens on the vehicle, acknowledged by the buyer

• Signatures of both parties

Illinois law doesn't require the bill of sale or the title to be notarized, which keeps the process fairly simple compared to some other states.

How the Bill of Sale Fits Into the Illinois Title Process

A private car sale in Illinois isn't complete once cash changes hands. Both the buyer and seller have separate follow-up steps, and missing either one can create real headaches down the line.

What the Seller Needs to Do

Once the sale is final, the seller's main job is protecting themselves from liability. This starts with removing the license plates — in Illinois, plates stay with the seller, not the vehicle. After that, the seller must file a Seller's Report of Sale (Form VSD 703) with the Illinois Secretary of State. Filing this promptly matters because, as the form itself notes, completing it does not meet the legal requirement for transferring ownership — Illinois law requires the vehicle owner to complete and sign the Assignment of Title section on the Certificate of Title to the buyer, who must then apply for a new title (source: ILSOS, Seller's Report of Sale — VSD 703).

What the Buyer Needs to Do

The buyer has a tighter timeline. All vehicles must be registered within 20 days of the purchase date, according to Illinois Secretary of State guidance (source: ILSOS, Vehicle Services). To complete registration, the buyer needs to visit a Secretary of State facility with the signed title, the Application for Vehicle Transaction(s) (Form VSD 190), and the applicable tax form.

For a private-party purchase, that tax form is Form RUT-50. Per IDOR, Form RUT-50 is due within 30 days of the date the vehicle is purchased or acquired by gift or transfer, and it's submitted to the Secretary of State when the buyer applies for title (source: IDOR, Private Party Vehicle Use Tax).

Illinois Private Party Vehicle Use Tax: What Buyers Actually Pay

This is the part most private-sale buyers get wrong — they assume tax is based on a flat percentage, like it is with a dealer purchase. It isn't. For private-party sales, Illinois uses a flat tax schedule tied to the vehicle's age or purchase price, laid out in the state's official RUT-5 chart.

If the purchase price (or fair market value) is under $15,000, the tax is based on the vehicle's model year:

Source: Illinois Department of Revenue, RUT-5 Private Party Vehicle Use Tax Chart for 2026

If the price or fair market value is $15,000 or more, the tax scales with the sale price instead — starting at $850 for vehicles priced $15,000–$19,999.99 and rising to $10,100 for vehicles at $1 million or more. A trade-in deduction is not allowed on this tax, and motorcycles, ATVs, and similar vehicles are taxed at a flat $25 regardless of value (source: IDOR, RUT-5 Chart).

This is exactly why the bill of sale matters so much in Illinois — it's your documentation of the agreed purchase price if the state ever questions what you reported on the RUT-50.

Title and Registration Fees to Expect

On top of the use tax, buyers pay standard title and registration fees to the Secretary of State. The title fee is $165 (source: ILSOS, Apply for Registration and Title), and a newly acquired vehicle with first-time plate issuance runs $151 for standard passenger registration on top of that (source: ILSOS, Passenger License Plates). Together, that's the baseline cost of getting a used car titled and plated in your name, before any use tax is added.

Where KarKiosk Fits In

If you're selling privately in Illinois, having clean paperwork and a clear asking price makes the entire process smoother — for you and for the buyer. KarKiosk is built for exactly this kind of private car sale in the U.S., helping sellers list their vehicle, connect with serious buyers, and move through the sale with less guesswork. Pairing a solid listing with a properly completed bill of sale means fewer questions at the Secretary of State counter and a faster path to getting paid.