KANSAS CITY, Mo. — American workers may soon start to see a boost in their take-home pay. That’s the result of lower tax rates signed into law last year by President Trump.

But you need to make sure these changes will be right for you come tax time next year.

If you have a big family or itemize your deductions, you may take home more now but could end up owing Uncle Sam because some tax breaks no longer exist or are limited by the new law.

“If I have a little extra money, I’m spending that,” Missy McCandless said.

McCandless likes the idea of taking home more money from her job as a dental hygienist. She said her family could always use more for her son or improving their home. She even has dreams of being able to use her tax windfall to take a family trip.

But, she’s not ready to do any of that yet.

“The only problem comes in when we look and say, ‘OK, we’re getting extra money back, but what are we going to owe?’ That’s the only scary thing. I would rather take that money away because it’s like I never really had it in the first place.”

Like most Americans, McCandless purposely withholds more from her paycheck to make sure she gets a big tax refund every year.

Her co-worker Cheryl Owens also isn’t convinced any increase she sees will make a difference in her life.

“No one wants to owe, especially not the IRS, so that is a little concerning,” Owens said.

The government says three out of four tax filers received refunds last year, averaging nearly $2,800 each.

Andrew Wagner, a senior tax adviser at H&R Block, said it’s the single largest financial transaction most Americans have every year.

“It has a huge impact on the average American,” he said. “A lot of people use that. It helps them budget. They have this huge refund they look forward to at the end of the year.”

Trump’s desire to put tax preparation firms like H&R Block out of business by reducing the federal tax form to a postcard didn’t materialize. In fact, the Kansas City-based firm said taxpayers may need help navigating a new tax structure now more than ever.

“If you do nothing, you’re likely to see a change in your paycheck, your take home pay, your net pay, on your pay stub,” Wagner said. “If you do nothing, you might be a little surprised by the amount you’re receiving in your take-home pay.”

A single worker earning $50,000 a year and claiming two allowances should expect to take home about $100 more a month. The Job Creators Network said those with children should expect even bigger increases.

Kelly McCracken, dentist owner of the Amazing Smiles dental practice, has payroll software that implements the reduced rates on her employees’ paychecks.

“It doesn’t change obviously what I pay them, but for me to do payroll through Quick Books, it does help to know how these changes will come down,” she said. “For every employee, it’s going to be different. That’s where it comes into a little bit of a gray area is figuring that out for each person.”

Ninety percent of workers will have bigger paychecks under reduced tax rates that must be implemented by Feb. 15.

“I get a lot of questions from people who are seeing changes in their paycheck, and they want to make sure they don’t want to owe a significant amount of money,” certified public accountant Kyle Nagy said. “They are just coming to me: ‘Can you give me a rough idea of whether this is good for me or bad for me?’

Accountants like Nagy say the key is the W-4 form, which determines how much tax is withheld from your pay. It’s based on whether your spouse works, the number of children in your home and other factors.

Right now, the form doesn’t take into account the elimination of deductions for dependents and a doubled-standard deduction that may make many taxpayers no longer eligible to itemize.

The U.S. Department of the Treasury is working on a new W-4, but it’s not expected to be ready until March.

“I think once the calculations are fine-tuned, then the public will generally see a reduction in the amount of tax withheld, and they’re not going to have a detrimental effect when they go to file their taxes next year,” Nagy said. “They should see similar results to what they are used to seeing in terms of balances due and refunds.”

The treasury department said most workers shouldn’t have to alter their tax withholding.

Still democrats have asked the IRS to make sure the take-home pay boost this year doesn’t result in eliminated or reduced refunds next year.