A toll gantry over the Massachusetts Turnpike. Photo courtesy of MassDOT

Out-of-state drivers are taking Massachusetts for a ride, to the tune of $26.8 million in unpaid tolls since the electronic system was implemented over two years ago, with Connecticut the biggest offender.

The tab has been steadily rising since the state switched to electronic tolling in October 2016, jumping by $7 million just in the last six months.

About $2.6 million of the owed amount has been charged within the last 30 days, which are not overdue and don’t have any fees attached. The remaining $24.1 million has been unpaid for a month or more, and $20.7 million of that hasn’t been paid in over 91 days as of Dec. 31.

That number has increased since the end of June, when the amount was around $17.1 million unpaid for a month or more, with an additional $2.3 million owed for under 30 days.

The state has agreements with Maine, New Hampshire, New York and Rhode Island to prevent people living in those states from renewing their license and registration if they haven’t paid the toll after 90 days. But they don’t have the same deal with Connecticut, which is the biggest offender, racking up 22 percent of the unpaid tolls.

New Hampshire residents account for 14 percent of unpaid tolls, followed by Rhode Island and New York which are tied at 11 percent and then Maine and New Jersey at 6 percent.

Over 2.5 million out-of-state drivers on the Mass Pike without an E-ZPass transponder paid through Pay By Plate accounts since the switch, forking over more than $73 million to the state, according to the MassDOT.

“These outstanding charges do not necessarily equate to lost revenue, as MassDOT has several measures in place to collect these funds,” MassDOT spokesperson Patrick Marvin said. “MassDOT is on track with revenue projections.”

The agency sends mail to the unpaid customers “several times,” according to Marvin, and regularly reviews billing details to ensure they have the right contact information.