Form W-4 helps employers determine how much federal income tax to take out of their employees' wages. On the form, employees state their withholding conditions, such as filing status, number of allowances and any additional amount they want withheld.

The IRS is encouraging taxpayers to make sure they're well-informed about their tax situation as the filing deadline approaches. The key topics include special steps related to charitable contributions, economic impact payments and advance child tax credit payments.