Every tax season, a lot of people feel like they’ve hit the lottery — except it’s their own money they are collecting.

Millions of workers calculate their withholdings so that they get money back at tax time. They know their employer is sending too much to Uncle Sam, and they like it that way. They don’t trust themselves to save. They count on the tax refund for any number of things, such as paying off debt or taking a vacation.

But Congress passed major tax legislation at the end of last year that could affect your refund if you are one of these folks, according to a recent report by the Government Accountability Office (GAO).

Under the Tax Cuts and Jobs Act, the Department of the Treasury had to establish new federal tax-withholding tables. The IRS publishes the withholding tables and employers use them to determine how much tax to withhold from an employee’s paycheck.

Each year, employers withhold more than $1 trillion in income tax from employees’ pay, including wages, bonuses and commissions, according to the GAO.

Sen. Ron Wyden, D-Ore., and Rep. Richard Neal, D-Mass., asked the GAO to review the revised federal tax withholding tables for 2018.

The overwhelming majority of people — 73 percent — will still be in a situation where too much is withheld, according to the GAO. Meanwhile, 21 percent of taxpayers might not be withholding enough from their paychecks to cover their tax bill.

For the 2018 tax season — from January to May — the IRS issued more than 102 million refunds totaling $284.9 billion. The average refund was $2,778.

Ideally, the goal is to have your withholdings match your actual tax obligation. You might owe a little or get a tiny refund. But the current withholding system is biased slightly toward over-withholding, the GAO says in its report.

So how do you hit the right withholding or something close to it?

Review your W-4 Employee’s Withholding Allowance Certificate. As a wage earner, you are required to pay federal income tax by having it withheld from your pay throughout the year. The amount is based on the number of allowances you claim on your W-4. Allowances are based on your anticipated tax deductions (mortgage interest, charitable gifts, deductible medical expenses, etc.). If your tax situation changes — you get married, have a child or purchase a home — you should fill out a new W-4 form.

You can calculate the right number of allowances by using the worksheet on the W-4. Or you can go to irs.gov and search for “Withholding Calculator.”

Do this soon, because we’re already more than halfway through the year. If you find you’re going to owe, you’ll need to catch up by increasing your withholdings.

To use the IRS withholding calculator, you’ll need your most recent pay stubs, a copy of your 2017 federal tax return and any information about deductions or credits you expect to take.

Once you’ve answered a series of questions, the worksheet or online calculator will suggest a number of allowances you should put down on a revised W-4 to give to your employer.

If you fall into the following groups you definitely should check what’s being withheld from your paycheck, according to Eric Smith, an IRS spokesman:

You’ve itemized in the past but might now opt to take the higher standard deduction under the new law. It’s going up to $12,000 for individuals, $18,000 for heads of households and $24,000 for married couples filing jointly.

You are a two-wage-earning household.

You have a complex tax situation.

You have a significant amount of outside income not covered by withholding.

You receive a pension. If you use the IRS calculator, treat your pension income like it’s a paycheck, Smith said. Or use the worksheet on form W-4P Withholding Certificate for Pension or Annuity Payments.

If you’re receiving Social Security, you may also need to review how much is being withheld from your monthly benefit, Smith said. In this case, you would use the worksheet on the W-4V, the voluntary withholding request form for unemployment compensation and certain federal government and other payments.

Don’t be daunted by this task. If the number you get looks funky, go back through to make sure you answered the questions correctly. Or consult a tax professional.

If you regularly get a refund, you need to perform a paycheck checkup now. And while you’re at it, maybe it’s time you stopped having too much money taken out.

— Washington Post Writers Group