Screenshot from a 2015 Turbo Tax commercial asking, 'Did you get married last year?'
Screenshot from a 2015 Turbo Tax commercial asking, 'Did you get married last year?' - 
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When Adena DeMonte first met her boyfriend Dan, he put one thing out on the table: one day, he wanted to get married. His own parents had never tied the knot, and he'd grown up wanting to have marriage in his life.

“So from day one of our relationship, we literally had this conversation,” DeMonte says. “I basically committed to him that not then, but one day, I would get married.”

Fast forward nine years, they've got good careers in the tech industry, an apartment together in Mountain View, California and DeMonte's starting to feel ready to make good on that marriage promise.

There's one thing you should know about her: she's a total finance nut. So much so, that she thought she'd broach the marriage conversation with Dan by talking about tax savings.

“Kind of to tease him a little bit,” she says. “'If we were married, we would save x number of dollars this year and next year.'"

But, when DeMonte looked up that number of dollars online, she discovered that if she and Dan got married this year, they'd actually pay about $1,000 more in taxes than they would as single people. If they both make more money down the line, they could get an even higher tax penalty for being married.

The idea that marriage might cost her tens of thousands of dollars some day, when those dollars might sustain her if she lost her job or wanted to stay home with kids, suddenly didn't seem very responsible — which was pretty tough news to break to Dan.

“We both said, 'Wow that's crazy that the government is actually saying that if you are two people making the same amount of money married, versus two people making the same amount of money separate, you're actually going to end up paying more,'” she says.

The marriage penalty comes from an attempt to make taxes fairer. Up until the 1940s, couples would file as individuals, but around World War II, when the top income tax rate was very high, some rich couples were figuring out a trick. Say one spouse made a $100,000 a year and the other made nothing. If they split it, report that each spouse made $50,000, they'd dodge the highest tax bracket. A good deal for them, but unfair to less-savvy tax filers.

“So the result in 1948 was actually just to accept that benefit, and give it to every married couple,"says Stephanie McMahon of the University of Cincinnati College of Law.

The government decided to let every married couple file jointly.

“Every married couple could shift income from one spouse and split it between both spouses,” McMahon says.

But single people started complaining about the fairness of filing jointly, questioning why married people got to save money on taxes. In 1969, McMahon says, single individuals managed to get a reduced tax bracket compared to joint filers.

This created the little-known singles bonus. But there's a problem, if someone is in a marriage where both people make a similar amount of money, they don't get any benefit from shifting their income between spouses. So, they pay more taxes than everyone else.

The cutoffs for certain tax benefits, like the Earned Income Tax Credit, are lower for two married people than they are for two single people. So lower-income married couples can get penalized too.

James Alm, an economist at Tulane University, found a small, but significant, impact of the marriage penalty on people's marriage decisions.

"A 10 percent increase in the marriage penalty decreases the likelihood of your getting married by one or two percent," he says.

But it's more about the principle of the thing to him.

“The main factor in regards to the marriage penalty is just kind of the notion of fairness,” he says. “Is it appropriate that people's taxes should change, positively or negatively, simply because they're getting married?”

Alm would prefer to return to a system where everyone files as an individual, a trend he sees in other countries right now.

Meanwhile, Adena DeMonte is still weighing her options.

“If anyone out there can convince me that I should get married, please do, because I want to get married. But it just doesn't seem to make a lot of sense right now," she says.

She says if Dan proposed today, she'd say yes. But instead of actually getting married, she'd ask to have a lawyer write up a marriage-like commitment agreement for them — which she admits, sounds terribly unromantic.