The IFTA agreement defines an IFTA qualified vehicle as:
1) A vehicle having two axles and a gross vehicle weight or registered gross vehicle weight exceeding 26,000 pounds;
2) A vehicle having three or more axles regardless of the weight;
3) A vehicle that used in combination (for example: tractor and trailer), when the weight of the combination exceeds 26,000 pounds.
Qualified vehicles do not include recreational vehicles.