For years, it’s been an open secret on the commuter rail. Buy a 12-ride punch card, and you can milk it for 14, 15, even two dozen rides.

Sometimes, it’s crowding on rush-hour trains, conductors too busy to reach everyone. Sometimes, it’s human error, errant punches by fast-moving hands. And sometimes, it’s done with a wink and a nod, the same box punched over and over, for the same people.

Those free rides are coming to an end. On July 1, the T plans to retire the 12-ride pass and its six-month expiration, replacing it with a 10-ride pass good for a mere 30 days - a lesser-known provision in the package of fare increases and service changes enacted last week, and taking effect July 1.

“It’s become clear over the years that for some people, there’s an expectation that you’ll get more than 12 rides out of a 12-ride ticket, and that’s something that we needed to address,’’ said Joe Pesaturo, a spokesman for the T.

The punch cards, depending on the line or destination, cost $20.40 to $99. The T sold $18.1 million of them last year; if each one enabled two free rides - a conservative estimate, according to those who boast of it and rail against it online - that’s $3 million.

No small sum, but a rounding error for an agency with a $1.7 billion budget.

But every dollar the T loses in fares must be made up with ad sales and tax support.

And free rides on the 12-ride pass are particularly infuriating for those with monthly commuter rail passes ($59 to $265; soon, $70 to $329), who prepay for unlimited rides that cannot be stretched beyond their month of use.

Fare evasion in all its forms - slipping on the back of a crowded Green Line trolley above ground, piggy-backing at station fare gates, and especially riding gratis on the pricey commuter rail - was a frequent complaint at the hearings the MBTA held across the region earlier this year.