The W-4 form you fill out when you start a new job helps your employer determine how much tax to withhold throughout the year. It lists the number of your dependents, your marital status and other factors that affect how much tax you'll owe each year. A mistake or incorrect form can result in too much or too few little being withheld, and can cost you money.
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Contact the IRS
If you notice that an incorrect amount has been withheld at the end of the year, or notice an error on your W-4 form, you should contact the IRS as soon as possible. Inform it of the error, then determine what the best course of action is. You might owe more money than what you have paid because of the error. In that case, make arrangements with the IRS to pay off your taxes as soon as possible. If money is owed to you, make sure you indicate that when you file taxes, or ask the IRS to grant you an extension so you can file correctly and recover the extra money you paid. You can call the IRS at 800-829-1040.
Fill Out a New Form
You will also want to fill out a new W-4 form when you notice errors at the end of the year. Fill out the new form completely and carefully to avoid making another mistake. Sometimes, if your handwriting is sloppy, it can result in critical errors on your tax withholdings. Consider filling out the form online via the IRS website rather than printing on the form.
Keep it Current
You should periodically review your W-4 form with your employer. Check the records with your HR department to ensure everything is current. For example, if your marital status changes, or if you move or have a baby, fill out a new W-4 form because all of those things can impact how much tax you owe and your withholdings throughout the year. Also, if your spouse changes jobs or your household income changes, fill out a new W-4 form. You can fill out a new W-4 form at any time, so you don't have to — and shouldn't — wait until tax time.
If you notice your W-4 form is incorrect at the end of the year, you should wait to file taxes until the issue is resolved. Remember, though, failing to file on time can cost you money in IRS penalties so don't wait until the last minute to address the issue. As soon as you notice an error, contact the IRS to address it so that when you file your taxes, you file for the correct amount.