If you sell your last truck, park the business, or otherwise stop operating taxable heavy vehicles, you stop owing Form 2290 tax. But the IRS also wants to know you are done, so it doesn't keep expecting a return.
What the IRS instructions say
In the IRS's words: "If you no longer have vehicles to report, file a final return. Check the Final Return box on Form 2290, sign the return, and mail it to the IRS."
Two things in that sentence matter. It applies when you no longer have vehicles to report — not when one truck of several is sold. And the return has to be signed: the IRS says an unsigned return isn't considered filed.
You don't have to mail it. The IRS e-file schema for Form 2290 has its own Final Return indicator, so a final return can be e-filed like any other Form 2290 — the instructions' "mail it" describes the paper route. Choose "This is my final return" on the return type step, and the return is transmitted with that box checked.
Claim what you are owed on the way out
If you paid tax on a truck for this period and then sold it, the tax for the remaining months can come back. A vehicle sold, destroyed, or stolen before June 1 and not used for the rest of the period qualifies for a credit on the next Form 2290 you file, or a refund on Form 8849.
For each truck, you'll need the VIN, its weight category, the date of the sale (or destruction or theft), the credit worksheet, and — for a sale — the buyer's name and address. The worked example is in claiming the credit for a sold, destroyed, or stolen truck.
One limit: the credit on Form 2290 can't be more than the tax on that return. If the return has little or no tax on it, the excess is claimed as a refund on Form 8849 with Schedule 6. The credits and refunds guide covers both routes.
Add each one in the credits step; the credit is figured from the IRS partial-period table.
If you sold a suspended truck
If a truck you reported as suspended (category W) is sold, you must give the buyer a statement showing your name, address, and EIN; the VIN; the sale date; the odometer reading at the start of the period and at the sale; and the buyer's name, address, and EIN. If you don't, you can remain liable for the tax if the truck later goes over the mileage limit. More in suspended vehicles and category W.
Records to keep after you stop
Closing the business doesn't end the recordkeeping. Keep records for every taxable vehicle registered in your name for at least 3 years after the tax is due or paid, whichever is later — even if a vehicle was in your name for only part of a period. For suspended vehicles, keep the records at least 3 years after the end of the period the suspension covers. For each truck, the records should show how and when you disposed of it, including the buyer's name and address if it was sold.
Starting again later
If you put a taxable truck back on the road, you file again for the month it is first used — the Form 2290 due date calculator shows the deadline.