Bill of Sale Aug 13, 2026
Buying or selling a used car in California comes with more paperwork than most people expect. A bill of sale sits near the bottom of that pile in terms of legal weight, but it is often the one document that saves you when a dispute pops up months later. This guide covers what a California bill of sale is, when you actually need one, what it must include, and how it fits into the state's title transfer, tax, and registration process.
What Is a California Bill of Sale?
A California bill of sale is a written record of a private vehicle transaction between a buyer and a seller. It documents the sale price, the date of sale, the vehicle's identifying details, and the signatures of both parties. The California Department of Motor Vehicles (DMV) publishes an official version, Form REG 135, and treats a properly completed bill of sale as a document that helps establish the chain of ownership, even though it does not replace the title itself.
Source: California DMV – Vehicle Industry Registration Procedures Manual, Bill of Sale (VC §1652)
Is a Bill of Sale Legally Required in California?
No. California does not legally require a bill of sale to complete a private-party vehicle sale. The signed Certificate of Title is what actually transfers ownership. That said, the DMV still provides a state-approved bill of sale form for anyone who wants one, and most experienced sellers use it anyway because it is the only written proof of the sale price, sale date, and buyer contact information if a question comes up later.
There are a few situations where a bill of sale is explicitly not required at all: sales between California-licensed dealers, and dealer sales to a retail buyer where the title has already been properly endorsed. Outside of those cases, using the DMV's form costs nothing and takes a few minutes.
Source: California DMV – General Registration Information, Bill of Sale
One practical reason to fill one out anyway: the DMV uses the sale price on the bill of sale to help calculate the Vehicle License Fee (VLF) at registration. Without a documented price, the DMV may fall back on the vehicle's approximate market value, which can push the fee higher than the actual purchase price.
What Information Must a California Bill of Sale Include?
Form REG 135 keeps things fairly simple, but every field matters. Skipping the odometer reading or leaving the sale price blank is the most common reason a bill of sale ends up useless in a later dispute.
| Category | Required Details |
|---|---|
| Buyer information | Full legal name and current address |
| Seller information | Full legal name, address, driver's license or ID/dealer number, and signature |
| Vehicle description | Year, make, model, and Vehicle Identification Number (VIN) |
| Plate / registration | License plate number or CF number |
| Sale details | Sale date and purchase price (or gift value and relationship, if applicable) |
| Condition disclosure | Whether the vehicle is sold “as is” or with a stated warranty |
How to Complete and Use Form REG 135
1. Negotiate the price and confirm the buyer's identity. Sellers should check a valid driver's license before filling in the form.
2. Fill out the bill of sale completely, including the current odometer reading for vehicles that require disclosure (more on this below).
3. Sign it. California does not require a notary public to witness or seal the signatures on a bill of sale or a title transfer.
4. The seller hands over the signed title, a valid smog certificate if one is required, and the keys. Standard plates stay with the car; toll transponders and custom plates should be removed first.
5. The buyer submits the signed title, bill of sale, smog certificate, and proof of insurance to the DMV, then pays transfer fees and use tax.
Seller Responsibilities After the Sale
Handing over the keys is not the end of a seller's job. California law requires sellers to notify the DMV within 5 calendar days of the sale using the Notice of Transfer and Release of Liability (Form REG 138).
This form can be filed online using the vehicle's license plate or VIN and the sale date, and it does not require any cooperation from the buyer. Filing online typically updates the DMV's record within one business day.
Skipping this step matters more than sellers realize. Until the Release of Liability is filed, the vehicle stays registered to the seller in the DMV's system, which means parking tickets, toll violations, or worse can technically still land on the seller's record.
Buyer Responsibilities After the Sale
Buyers have 10 days from the purchase date to register the vehicle and complete the title transfer at a California DMV office.
Because California does not have a general sales tax exemption for private-party car sales, buyers owe use tax at registration, calculated the same way sales tax would be. The statewide base rate is 7.25 percent, but county and city district taxes are added on top, and the combined rate is based on where the buyer lives, not where the car was bought.
That last point trips a lot of people up. A San Francisco resident who buys a car from a private seller in Sacramento still owes San Francisco's district rate, not Sacramento's, because California sources use tax to the buyer's registration address.
| Location | Combined Sales/Use Tax Rate |
|---|---|
| Statewide base rate | 7.25% |
| Sacramento (city) | 8.75% |
| Los Angeles County | 9.5% |
| Alameda County | 10.25% |
Odometer Disclosure and Smog Certification Requirements
Federal and California law both require sellers to disclose the odometer reading at the time of sale for most vehicles. Following a 2021 update from the National Highway Traffic Safety Administration, disclosure is now required for vehicles up to 20 model years old, not 10. In practical terms, a 2011 model-year vehicle still needs an odometer disclosure through 2031, while model-year 2010 and older vehicles are exempt.
Source: California DMV – Vehicle Industry News, New Odometer Disclosure Requirements (VIN 2021-10)
Smog certification is a separate requirement. Most vehicles more than 4 model years old need a valid smog certificate completed within 90 days of the sale before ownership can transfer. In a private sale, the seller is usually the one responsible for obtaining it, and some newer vehicles and EVs may be exempt.
Common Mistakes to Avoid
• Leaving the sale price blank — this can push the buyer's Vehicle License Fee higher than necessary.
• Skipping the Release of Liability filing — the seller can stay on the hook for tickets and violations until it's filed.
• Forgetting the odometer disclosure on 2011-and-newer vehicles, which the DMV will reject paperwork over.
• Assuming a notary is required — it isn't, for either the bill of sale or the title signature.
• Not double-checking that the VIN on the bill of sale matches the VIN on the title exactly.
Bill of Sale for Gifts and Family Transfers
If a vehicle changes hands as a gift, the bill of sale should note that clearly, along with the relationship between the parties and the vehicle's value. Family transfers between qualifying relatives — parent, child, grandparent, grandchild, spouse, registered domestic partner, or sibling — can be exempt from use tax when filed with a completed Statement of Facts (Form REG 256). The exemption does not extend to aunts, uncles, cousins, or in-laws.
Final Thoughts
A California bill of sale won't transfer ownership by itself, but it's cheap insurance against a dispute over price, date, or condition down the road. Filling out Form REG 135 completely, filing the Release of Liability on time, and keeping the odometer and smog paperwork in order covers most of what either side needs to walk away clean from a private sale.
If you're getting ready to sell or buy a used car in the U.S., KarKiosk is built around exactly this kind of private-party transaction, from listing a car to getting the paperwork right.
