Idaho Form ST-133 is the sales tax exemption certificate used for two kinds of vehicle transactions: a motor vehicle sold between close family members, and a titled vehicle or vessel sold to an enrolled member of an American Indian tribe and delivered on a reservation. It is not a general-purpose exemption form, and it will not cover resale purchases, nonprofit buying, or production equipment. If your transaction fits one of the two situations above, the form is short, the buyer and seller complete it together, and the seller keeps it on file rather than sending it to the state.1Idaho State Tax Commission. Form ST-133 Sales Tax Exemption Certificate Family or American Indian Sales
Who Qualifies for the Family Motor Vehicle Exemption
Idaho Code 63-3622K exempts certain motor vehicle sales between close family members from the state’s 6% sales tax. Three conditions all have to be true before you can use ST-133 to claim it.
First, the item has to be a motor vehicle. Vessels, ATVs, UTVs, specialty off-highway vehicles, off-road motorcycles, snowmobiles, and trailers are not covered, even when the sale is between a parent and child.1Idaho State Tax Commission. Form ST-133 Sales Tax Exemption Certificate Family or American Indian Sales
Second, the seller must have paid sales or use tax when they originally acquired the vehicle. If the seller got it tax-free for any reason, the family exemption drops out and the current sale is taxable.2Idaho State Legislature. Idaho Code Section 63-3622K – Sales Tax
Third, the buyer and seller have to be related within the second degree of consanguinity. That means parent and child, grandparent and grandchild, or brother and sister. Aunts, uncles, cousins, and in-laws do not qualify. There is one wrinkle for married couples: if the vehicle is community property, either spouse can sell it to a qualifying relative of the other spouse and the exemption still applies. So your spouse’s parent can buy a jointly owned car from you tax-free, even though the two of you are related only by marriage.1Idaho State Tax Commission. Form ST-133 Sales Tax Exemption Certificate Family or American Indian Sales
Who Qualifies for the American Indian Exemption
The second use of ST-133 is for sales of titled or registered vehicles and vessels to enrolled tribal members. Unlike the family exemption, this one covers vessels as well as motor vehicles. Two things have to be true.
The buyer must be an enrolled member of an Indian tribe, and the seller must see proof of enrollment before completing the sale. A tribal identification card issued by the tribe is acceptable documentation.1Idaho State Tax Commission. Form ST-133 Sales Tax Exemption Certificate Family or American Indian Sales
The seller must also deliver the vehicle or vessel to the buyer within the boundaries of an Indian reservation. A sale completed off-reservation does not qualify, no matter the buyer’s tribal status. Both the buyer and the seller sign the form to certify where delivery actually took place. The Tax Commission treats delivery location as a factual question during audits, and a certificate claiming reservation delivery that cannot be supported can expose both parties to back tax and penalties.
Filling Out the Form
You can download the current ST-133 from the Idaho State Tax Commission website. Have the vehicle details and identification for both parties on hand before you start.
Vehicle and Party Information
The top of the form takes the year, make, model, and vehicle identification number, or hull identification number for a vessel. Below that, both the buyer and the seller fill in a name, address, phone number, and either a driver’s license number with state of issue or a taxpayer identification number.1Idaho State Tax Commission. Form ST-133 Sales Tax Exemption Certificate Family or American Indian Sales
Family Sale Section
For a family claim, the form walks through three yes-or-no questions: Is the vehicle a qualifying motor vehicle? Did the seller pay sales tax when they acquired it? Is there a qualifying family relationship? If any answer is no, the form instructs you to stop, because the exemption does not apply. You then mark the specific relationship: parent and child, grandparent and grandchild, or brother and sister.
American Indian Section
For the tribal member exemption, you enter the name of the reservation where delivery occurred, the name of the tribe in which the buyer is enrolled, and the buyer’s tribal identification number. The seller should verify the tribal ID before signing.
Signatures
Both parties must sign and date the form. An unsigned certificate is invalid. By signing, the buyer and seller certify under penalty of perjury that the information is accurate and the exemption applies.
What the Seller Does With the Form
ST-133 is never filed with the Idaho State Tax Commission as part of the sale. It stays in the seller’s records and only comes out if the Commission audits the transaction. Under Idaho Administrative Rule 128, every sale in Idaho is presumed taxable unless the seller has a properly completed exemption certificate on file, so if there is no valid ST-133, the burden falls on the seller to prove the sale was exempt.3Justia Regulations. Idaho Administrative Code 35.01.02.128 – Certificates For Resale And Other Exemption Claims
To hold up at audit, the completed form must be legible and include a date, the buyer’s name and signature, the buyer’s address, and an EIN or driver’s license number. A certificate missing any of those elements may not protect the seller.3Justia Regulations. Idaho Administrative Code 35.01.02.128 – Certificates For Resale And Other Exemption Claims
Sellers should keep the completed certificate for the length of any ongoing relationship with the buyer plus four years after that. The Idaho State Tax Commission has stated this retention standard for exemption certificates generally.4Idaho State Tax Commission. Recordkeeping for Printing and Publishing For most private family vehicle sales, which are one-off transactions, that works out to at least four years from the sale date.
If an auditor finds the certificate missing or incomplete, the seller can be assessed for the uncollected tax plus interest from the original due date, and late-payment penalties can reach 25% of the tax owed.5Idaho State Tax Commission. Sales Tax Filing and Paying
Mistakes That Void the Exemption
The most common error is using ST-133 for the wrong kind of transaction. Businesses sometimes hand this form to vendors as if it were a general exemption certificate. It is not. A seller who accepts an ST-133 for a non-vehicle purchase, or for a vehicle sale that does not involve a qualifying family or tribal member, ends up with no valid exemption documentation at all.
Family sales get tripped up two ways. The property does not qualify (selling an ATV, trailer, or snowmobile to a sibling, for instance), or the relationship does not qualify (a sale to a cousin or an in-law falls outside the second-degree-of-consanguinity rule even though it feels like a family transaction).
For the tribal member exemption, the usual failure is delivery location. If the buyer drives to the seller’s lot off-reservation and takes possession there, the exemption does not apply, even if the buyer is a fully enrolled tribal member. Delivery has to happen inside reservation boundaries, and the form requires both parties to certify that it did.
If You Actually Need the General Exemption Certificate
If your situation is resale, a production exemption, a purchase by an exempt organization, or any other everyday sales tax exemption, ST-133 is not the right form. Idaho handles those on Form ST-101, the Sales Tax Resale or Exemption Certificate, which cannot itself be used for vehicle or vessel purchases.6Idaho State Tax Commission. Form ST-101 Sales Tax Resale or Exemption Certificate Download ST-101 from the Idaho State Tax Commission and use it for those transactions instead.