BOSTON -- For months the Massachusetts Registry of Motor Vehicles has been dealing with budget cuts and registry closings. It even tried to charge customers for in-person service, until a legislative outcry led the governor to put a stop to it.

An investigation by Team 5 Investigates found the registry may be missing out on millions of dollars in revenue in commercial plate registration fees.

"They are just driving around and nobody pays attention to it," said Ralph Spears, a properties manager who pays the high cost of commercial plates. Spears is not happy that so many drivers who should pay, do not.

At two Home Depot stores, Team 5 Investigates found some contractor vehicles had commercial plates, but just as many did not.

Attorney John Scheft teaches police about motor vehicle law. He said the criteria and exemptions in the commercial license codes are too complicated for drivers to understand and not a priority for police to enforce.

"Any vehicle that's over 6,000 pounds, if you have business advertisements of markings on your vehicle, if you are using your vehicle for business and you are hauling goods, merchandise or equipment, you need to have a commercial plate," said Scheft.

It's projected that commercial plates will bring in $141 million this year, but there's no way to know how much more the state is missing from people who don't register commercially.

Registrar Rachel Kaprielian said she's not aware of any widespread revenue loss regarding commercial registration, but said the RMV "does extend a measure of trust that drivers will correctly register their vehicles and everyone will pay their fair share."

"They close down registry branches and they are increasing fees for everybody," said Spears. "If more people had commercial plates, they wouldn't have to raise the fees for everyone else."

Scheft said he didn't believe people are intentionally avoiding commercial registration. He said the registry needs to simplify the rules and regulations.