As an IRP registrant, you and the retailers or dealers you work with must keep records from the sale or lease of motor vehicles, trailers and glider kits you buy without paying tax under the IRP exemption.
Sellers
Dealers and retailers that sell or lease motor vehicles, trailers or glider kits under the IRP exemption must have the buyer complete a 
Form ST-104IC – Sales Tax Exemption Certificate – Interstate Commerce Vehicles. Dealers and retailers must keep a copy of the completed Form ST-104IC for at least four years.
Buyers
- When you buy a motor vehicle, trailer or glider kit exempt, you must keep records to verify that at least 10 percent of the IRP fleet mileage is outside Idaho for each reporting period.
- Keep records that show you paid tax on repair parts you bought in Idaho for qualifying motor vehicles, trailers and glider kits.
- Maintain normal books of account.
- Keep documents that support entries in the books of account.
Examples:- Bills
- Receipts
- Invoices
- Job or work orders
- Lease contracts
- All schedules or working papers used to prepare your tax returns
Your records must include:
- The total purchase price of anything you bought, leased or used in your business
- The amount of sales tax you paid to a vendor or use tax you paid on your tax return
- All sales and use tax returns
Keep all sales and use tax records for at least four years. If you don’t file returns, you should keep your records for seven years.