Idaho Bill of Sale Rules for Vehicles and Vessels: Deadlines and Tax

An Idaho bill of sale records the price, the parties, and the property in a private vehicle or vessel transaction. You need one whenever the seller has not written the purchase price directly on the certificate of title, and the same signed document acts as a 72-hour temporary operating permit that lets you drive the vehicle home before you register it.¹

When You Actually Need One

Idaho does not force a bill of sale onto every private sale. If the seller writes the selling price on the title, signs it, and dates it, that alone does the work. A separate bill of sale becomes necessary in three situations: the seller left the price field blank, the seller has not signed off their interest on the title, or the buyer needs a temporary permit to drive the vehicle before registering it.²

The document also drives tax collection. The county assessor uses the documented price to calculate Idaho’s 6% sales tax on the transfer. With no bill of sale and no price on the title, the assessor defaults to the NADA Official Used Car Guide’s average trade-in figure for a vehicle of the same make, model, year, mileage, and condition. That NADA number often runs higher than a real private-party price, so recording the actual price protects you from overpaying tax.³

Driving the Vehicle Home: The 72-Hour Permit

A signed bill of sale or properly assigned title works as a legal 72-hour permit to drive a newly purchased vehicle on Idaho public roads without plates. Weekends and state holidays do not count against the clock, so a Friday purchase runs through Wednesday. The permit covers noncommercial vehicles and unladen commercial vehicles. Laden commercial vehicles need a separate permit under Idaho Code § 49-432.¹

Keep the paperwork in the vehicle during that window. If you are pulled over, it is your only proof that you own the vehicle and can lawfully drive it unregistered.

What Goes on a Vehicle Bill of Sale

Idaho publishes a standard form, ITD 3738, available at county assessor offices and on the Idaho Transportation Department’s website. Any written document that captures the required information will work, but the state form makes sure nothing is missed.⁴

Every vehicle bill of sale needs to include:

The VIN, model year, make, and model of the vehicle
The actual sale price, which the assessor uses to calculate 6% sales tax
Full legal names and current physical addresses for the buyer and the seller
Both signatures and the date of the transaction

Notarization is not required. Some parties still choose to notarize for extra security, and Idaho law caps notary fees at $5 per act.⁵

Vessels and Boats

Watercraft sales run through the Idaho Department of Parks and Recreation rather than the Transportation Department, and the paperwork looks a little different.⁶

A vessel bill of sale should list:

The Hull Identification Number (HIN) stamped into the hull, which functions like a VIN
Manufacturer, year built, overall length, and propulsion type (inboard, outboard, or non-motorized)
The sale price, so the county clerk can calculate fees and applicable tax
Full legal names, addresses, and signatures of both parties

Propulsion type affects how the vessel is classified for licensing. Local rules can vary with the size or type of boat, so check with your county assessor before filing.

Sales Tax and the NADA Value Question

Idaho charges 6% sales tax on vehicle purchases, and the taxable amount takes in any document fees or other seller services rolled into the deal. You pay the tax at the county assessor’s office when you apply for the new title.³

If your reported price looks unusually low next to the NADA average trade-in value, the assessor flags the transaction for review by the Idaho State Tax Commission. You can sign an indemnifying affidavit swearing to the stated amount, but the Tax Commission may audit it. With no bill of sale in the file at all, the assessor simply uses the NADA figure, which typically sits above what private buyers actually pay.³

Gifted vehicles are outside sales tax because there is no purchase. The recipient still needs to file an Idaho Sales Tax Exemption Certificate (Form ST-133) with the county clerk when titling and registering. If the vehicle’s fair market value exceeds the federal annual gift tax exclusion of $19,000 per recipient for 2026, the giver may need to file IRS Form 709, though federal gift tax is generally not owed until lifetime gifts exceed the unified credit.⁷

Odometer Disclosure

Federal law requires the seller to give the buyer a written odometer reading whenever ownership changes. The seller records the exact mileage on the title and marks whether the reading is accurate, whether the odometer has been tampered with, or whether it exceeds its mechanical limits. Vehicles from model year 2011 and later carry this requirement until they reach 20 model years of age. Vehicles from model year 2010 and earlier follow the previous 10-year rule. Vehicles over 16,000 pounds gross weight are exempt.⁸

Odometer fraud is a federal crime. NHTSA investigations have produced prison sentences of up to 10 years along with substantial fines and restitution.⁹

Filing Deadlines for Buyer and Seller

The Buyer’s 30-Day Window

Buyers must bring the signed title and bill of sale to the county assessor’s motor vehicle office within 30 days of the transfer. Miss that window and a $20 late-filing penalty attaches on top of the standard title fees.¹⁰ For a vehicle bought out of state, the 30 days start when the vehicle first enters Idaho.

Every county charges the $14 statutory title fee, and most add a county administrative fee. Totals range from $14 in counties with no admin fee, such as Bannock and Caribou, up to $32.75 in Blaine County, with most counties falling between $19 and $25. The Idaho Transportation Department publishes the full fee schedule.¹¹

The Seller’s 5-Day Release of Liability

Sellers should file a Release of Liability (Form ITD 3858) within five days of handing over the vehicle. Filing removes your name from the active registration and cuts off your exposure to traffic violations, towing charges, property damage claims, and injury claims tied to the vehicle after the sale. The filing fee is $3.50, payable by check or money order to the DMV, and the form goes to your county assessor’s motor vehicle department.¹² Until you file it, state records still tie you to the vehicle.¹³

Penalties for False Information

Idaho treats a false statement on a bill of sale, title application, or sworn statement of ownership as a felony. Understating the sale price to cut the tax bill falls squarely within that statute, as does using a false name or fictitious address. The savings on 6% tax are not worth felony exposure.¹⁴

If the assessor thinks the reported price is too low, the transaction gets flagged and sent to the Idaho State Tax Commission for review. The safer path is to report the actual price and, if the number draws questions, provide a sworn indemnifying affidavit explaining the circumstances behind a below-market sale.³

1
Idaho State Legislature. Idaho Code 49-504 – Issuance of Certificate of Title
2
Bingham County Idaho. DMV FAQ
3
Idaho State Tax Commission. Sales and Use Tax Guide for Vehicle Transactions
4
Idaho Transportation Department. Motor Vehicle Bill of Sale Form ITD 3738
5
Idaho Secretary of State. Notary Public – Frequently Asked Questions – General
6
Idaho Department of Parks and Recreation. Registration and Permits
7
Internal Revenue Service. What’s New – Estate and Gift Tax
8
Federal Register. Odometer Disclosure Requirements
9
National Highway Traffic Safety Administration. Odometer Fraud
10
Idaho State Legislature. Idaho Code 49-504A – Penalty for Late Filing
11
Idaho Transportation Department. County Registration and Title Fees
12
Idaho Transportation Department. Notice of Release of Liability
13
Idaho State Legislature. Idaho Code 49-526 – Release of Liability Upon Transfer of Vehicle
14
Idaho State Legislature. Idaho Code 49-518 – Altering or Forging Certificate of Title