[This post has been updated]

With the start of a new month and a new year, some Metro riders are doing a double take when they look at the dollar figure displayed on the digital readout at the fare gates.

What many are seeing is the combined effect of changes in the transit benefits and the effort by benefits administrators to comply with a long-standing IRS rule.

What they’re not seeing: The Metro fares didn’t increase. The readout at the fare gate may in some cases show riders a much different number than what they saw the last time they used their SmarTrip cards. But that wasn’t the result of Metro sucking more money off the cards.

Transit benefit: Congress didn’t extend the temporary cap of $230 a month on tax-exempt transit benefits included in the federal stimulus bill. So as soon as 2012 began, the benefit limit shrank to $125 a month.

That affected people in different ways, depending on whether they receive a direct transit subsidy, as many federal employees do, or they just tell their personnel offices to assign a certain amount of their paychecks for tax-exempt transit commuting, as many private employees do.

Auto load: This is another train that’s been coming down the track for transit benefits users. SmarTrip has gotten somewhat smarter, and is now able to load benefits directly onto the cards at the fare gates. So to add the value of the benefits to a card, you don’t have to wait in line at the vending machines each month.

SmarTrip purses: There’s a third element at work combining the technology upgrade and IRS rules. The technology may be new, but the IRS rule isn’t. It’s just taken Metro and the transit benefits program a long time to bring the two together.

The IRS wanted a better way of tracking how people use the tax benefits and subsidies, so that public money goes for the intended purposes.

The bottom line is that many people’s cards now contain three “purses.” (That’s what Metro and the benefits people call them. You can think of them as billfolds, or folders.) Your commuting money is divided three ways: A transit-riding benefit, a parking benefit and the cash you added to your card on your own.

The transit riding benefit is the amount up to $125 that can be used to ride Metrorail, Metrobus and many suburban transit systems.

The parking benefit is the amount up to $240 that can be used for Metro parking.

When you tap your card at a fare gate or at a bus fare box, you see the amount of your transit benefit. When you use the card to exit a Metro parking area, you see the parking benefit displayed. You assigned the amount of money in each of those two purses, but each will get drawn down at different rates as the month goes on.

If you hit bottom in either purse, the card will start drawing from the third purse, the one that contains the value that you added to the card on your own, outside the context of the benefits programs.

For people who don’t participate in the benefits programs, that’s the only purse they have to pay for everything, so keeping track of changes is relatively simple. Just as before, they can keep up to $300 in the private purse.

But for benefits participants, there are several challenges. For one thing, they get spooked when they see an amount displayed that’s lower than what they put in under the old system.

Maybe before they left for Christmas vacation they had $200 in stored value on the card, but this morning, they tapped on the fare gate and saw only $125 in the readout.

What they saw was the transit benefit readout for January. The value they had stored on the card previously should still be in their personal purse and available for use after they’ve exhausted the new transit or parking benefit for this month.

But if, on the other hand, they don’t use up all the monthly transit or parking benefit assigned to their cards under the new system, then it will be up to their employers to decide what to do with the leftover value.

So it’s best to check with your own personnel office, and to check your benefits account online, at smartrip.com. If you have already registered your account, click on “Manage your account online,” and you’ll be able to see the value available in each of your three purses. (You also can add value to your personal purse online.)

At the fare gates, fare boxes and the parking payment machines, you won’t see the value remaining in all three purses, only the amount in the purse appropriate to that particular use of the SmarTrip card.