Thousands of straphangers across the five boroughs could save hundreds on their MetroCard purchases come the new year.

In two weeks, a local law passed by the City Council in 2014 will require any business in New York City with more than 20 workers to let employees pay cover transit expense with pre-tax money.

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The program takes advantage of a federal that has operated voluntarily and lets riders spend up to $130 in tax-free income a month for mass transit expenses. 

In New York, that means bus and subway, Metro-North and Long Island Railroad riders can all qualify for what advocates project say can save commuters up to $443 a year on monthly MetroCards.

When the federal government opens up opportunities like this, local governments like our should take advantage," said Manhattan City Councilman Dan Garodnick, who ushered the bill through, at Union Square on Sunday. "This will be a real boon for New Yorkers."

An estimated 450,000 people who work in New York City will now be eligible for the benefit. Employers then either offer their workers a prepaid card or a debit card only usable at MTA vending machines.

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Any employee — whether they live in the city but work for a company based in the boroughs — who believes they are eligible and are not receiving the benefit can file a complaint with the Department of Consumer Affairs.

"We always give an employer the opportunity to come into compliance," said Amit Bagga, deputy commissioner for the agency.

An earlier version of the bill would have extended the tax break to 605,000 New Yorkers, but supporters still say the bill can actually save companies about $103 a year per employee who takes part in the program.

"The law will only work if riders know about it," said Rebecca Bailin, campaign manager with advocacy group the Riders Alliance. "That's why we're talking to riders and helping folks estimate how much they can save with pre-tax transit benefits."