Here's how to make your paycheck bigger in 2021

Pay raises can be hard to come by, especially now. But if you received a big tax refund this year, getting more take-home pay next year could be a matter of filling out a form.

That form is the W-4, and it has a big influence on how much tax comes out of your paycheck. Routinely having too much tax withheld is often the cause of big tax refunds, according to the IRS. Changing what's on your W-4 form can make it possible to skip the monthslong wait for a tax refund and boost your monthly take-home pay instead.

For families struggling to pay bills, having more cash now rather than later can be a game-changer. "If you have someone that had a huge refund last year, but maybe day-to-day expenses, groceries and stuff like that were a little bit tight, then [they] could adjust the W-4 to have less withheld so they would have more in their check every two weeks," said Adam Traywick, a certified public accountant in Fort Worth, Texas.

Seeing the connection between day-to-day financial life and what's on a W-4 can be hard. Linda Rogers, a certified financial planner at San Diego-based Planning Within Reach, recalls a client who was racking up credit card debt little by little every month because of trouble making ends meet.

"It was costing them money, and they were feeling bad about themselves for not being able to live within their means. It was just this situation where even though it feels good to get a refund, it's not what you should be doing."

To home in on how much to withhold, Rogers suggests first estimating how much income tax you will owe for the year. An online tax estimator or a tax pro can help you. If your financial situation hasn't changed much in the last year, you could also look at your previous year's tax return, Traywick said. That can help you get an idea of whether you are withholding too much.

The IRS website has a withholding estimator that can also help do the math.

You can review your paycheck after you have changed your withholdings to make sure your take-home pay is in line with what you were expecting, and if it isn't, you can fill out another W-4 and adjust things again, Traywick said.

But tread with caution. "You don't want to lower your withholding so you get a bigger check but then have to wind up owing the government money that you don't have," he said.