Sen. Chuck Schumer vowed to attach a popular commuter mass-transit tax break to legislation that would renew the US payroll tax cut.

Last year, 500,000 city straphangers and suburban-rail commuters were able to set aside $230 each month before taxes to cover the cost of their trips.

When that measure expired on Dec. 31, the benefit was capped at $125 a month.

“The last thing we should be doing in this economy is making it more expensive for New Yorkers to get to work,” said Schumer.

“The fact that this tax credit expired as the clock struck 12 on New Year’s is unacceptable, and I’m going to do everything I can to see the full extension of these commuting benefits.”

Companies also benefit from the transit break because they don’t have to pay payroll taxes on the amount of money set aside.

Congress has renewed the transit tax credit retroactively in prior years.

If extended, the transit benefit would cover the full $104-per-month costs of an unlimited 30-day MetroCard for city subways and buses and a substantial portion of Long Island Rail Road and Metro-North monthly commuting costs, Schumer said.

Metro area commuters saved $200 million last year from the transit credit and employers have saved $45 million since the benefit went into effect.