SPRINGFIELD, Mo. – A KOLR 10 Investigation reveals which overlooked tax credit Americans are missing out on, causing them to leave millions of dollars unclaimed.

Americans are behind last year when it comes to filing their tax returns. According to the IRS, 3% fewer workers have filed so far this year compared to last, or about a million people. Data from the IRS also shows families are leaving millions of dollars unclaimed.

“It’s just a big equation,” Janelle Grimm, a regional manager at Jackson Hewitt in Springfield told us.

Thomas Howell is a customer at one of her branches.

“Tax returns, the fun time of the year. Yeah, I’m so excited,” Howell joked sarcastically.

Like many of us, Howell would prefer a little help solving that tax equation.

“If we have anything coming, of course we want to be treated fairly,” Howell said.

But according to the IRS, collectively, taxpayers are leaving millions of dollars off their returns, and that’s from just one credit. Ray Roach is an agent at H&R Block, and knew which credit we were talking about.

“Earned Income Credit is probably the number one refundable credit,” Roach said. “Big thing that people miss out on, is they think any income will do it. But the terminology is earned, so you have to have a W-2 or your own business income for it to even kick in.”

In 2016, the US government paid $67 billion to 27 million workers through the EITC. Last year, 25 million people got $63 billion from it. Families with three kids could’ve missed out on thousands.

“Up to $6,557,” Grimm said, while pointing out the average refund for EITC is much lower than that.

These statistics make accountants worry that similar credits may also be overlooked.

“The Child Tax Credit will reduce my taxes by up to $2,000 per child,” Roach said. “If I don’t use it all there, then the additional tax credit kicks in, which is refundable.”

Tax overhaul under the Trump administration came with a new 1040 form.

“It went from 79 lines down to 24,” Grimm said.

She believes it could cause some people to make mistakes because they don’t see the potential credit now located on a separate worksheet.

“Because when you’re looking at a 1040 and you see these things, it brings to mind things you need to look for,” she said.

Watch out for recent changes to the W-4 as well, which could mean you’ve been getting more money per paycheck, and will get less back on your federal refund. Knowing his equation is now complete, and shipped off to the IRS helps Howell rest easy.

“That’s all part of the assurance to make you feel better, and help me sleep at night with my pillow,” Howell said.

If you did qualify for a child tax credit and will be getting money back, the PATH Act held those funds until about a week ago. That’s because fraud is more likely on those kinds of returns. As of Feb. 22, the government has started releasing that money. Tax returns should be submitted by April 15.