If your employer didn't withhold the right amount of federal taxes, contact your employer to withhold the right amount for the future. When you file your return, you will owe the amounts that your employer should have withheld during the year as unpaid taxes. If you're an employee, your employer is likely to withhold income tax from your paycheck and pay it to the IRS on your behalf. With every paycheck, your employer withholds part of your earnings to pay taxes.
If an excessive amount is withheld, it's true that you'll get a refund, but if you think about it, by waiting until tax season to request the return of that money, you've basically given the IRS an interest-free loan during the year. On the other hand, if you owe taxes when you file your return, you may have to work hard to pay what you owe, and you could also owe interest and penalties to the IRS if you haven't withheld enough during the year. This tax will apply to any form of income that summarizes your income, whether from employment or from capital gains. But more importantly (as far as the IRS is concerned), withholding helps the government ensure that you pay your tax bill every year.
One more reason why federal income tax wasn't withheld from your paycheck could be because you're completely exempt from paying income taxes. For example, tax withholding is no longer calculated based on the number of deductions, but based on the factors listed above. That said, keep in mind that just because you're exempt from federal income tax doesn't mean you're also exempt from all other taxable wages. Many people don't know how to determine if they need to withhold federal income taxes from their paychecks.
The W-4 form that you fill out for your employer when you start a new job determines the amount of income tax that will be withheld from your paycheck and, ultimately, the amount of taxes you will owe or return as a refund when you file your taxes. Withholding taxes can get pretty complicated if you're working remotely, in a different state than your employer. If you don't pay your taxes by withholding or don't pay enough taxes that way, you may have to pay the estimated tax. This method should give you the most accurate picture of your annual tax liability, but it will also take longer.
If it's so early in the year that you haven't received any paychecks yet, you can simply divide your total tax liability for the year that just ended by the number of paychecks you receive in a year. Keep in mind that just because the government sent you a refund check last year doesn't mean you don't owe any taxes. Once you know how much you'll owe in federal taxes, the next step is to determine how much you should have withheld per pay period to reach, but not exceed, that goal before December. Withholding does not include Social Security and Medicare taxes, which are called FICA (Federal Social Security Contributions Act) taxes.
When you declare yourself exempt from federal withholding, the government will stop withholding federal income taxes from your paychecks.