Withholding Tax: The Basics

The Federal income tax is based on a “pay-as-you-go” system. There are 2 ways to pay as you go: withholding tax or estimated tax. This article discusses withholding tax (also referred to as “tax withholding”).

​If you work at a job, your employer most likely withholds income tax from your paychecks. (Tax may also be withheld from other types of income – such as commissions, bonuses, and pensions.) The tax withheld is sent to the IRS on your behalf, and the funds are applied to your Social Security, Medicare, and income taxes for the year. The amount withheld in each category is reported on your Form W-2 (Wage and Tax Statement), which you receive from your employer.

How Is Withholding Tax Determined?

The amount of tax withheld from your regular pay depends on 2 things: how much money you earn and the information you give your employer on Form W-4 (Employee’s Withholding Allowance Certificate).

Withholding Social Security Tax and Medicare Tax
Social Security and Medicare taxes are automatically withheld by your employer and have fixed rates. The Social Security tax rate is currently 6.2% for the employer and 6.2% for the employee (12.4% total). The Social Security tax has a wage base limit of $128,700 for 2018. This means that most employees are required to pay 6.2% Social Security tax on the first $128,700 of their wages.
The Medicare tax rate is currently 1.45% for the employer and 1.45% for the employee (2.9% total). In general, an employee must pay 1.45% Medicare tax on the first $200,000 of their wages.

Withholding Federal Income Tax
The amount of Federal income tax withheld from your pay is based on the information you provide on Form W-4. When you start a new job, you are required to fill out Form W-4 and give it to your employer. If you need/want to make changes to your withholding tax at any point during the year, you must complete a new Form W-4.

For example, if you find that too much (or too little) tax was withheld last year, you can fill out a new Form W-4 to adjust your withholding. Additionally, certain life events (such as marriage, divorce, or the birth of a child) may change your filing statusor the number of exemptions you can claim. In these cases, you will need to give your employer a new Form W-4 to adjust your withholding status and/or number of allowances.

On Form W-4, there are 3 main types of information that your employer will use to calculate your withholding tax:
• Your withholding status (tells your employer whether to withhold at the “single” tax rate or the lower “married” tax rate)
• The number of withholding allowances you claim (each allowance reduces the amount of tax withheld)
• Whether you want an additional amount withheld

The more allowances you claim, the less income tax your employer will withhold. Claiming “0” allowances means you will have the most tax withheld from your pay. Based on your withholding status and allowances, your employer will use the IRS’ Income Tax Withholding Tables to determine how much Federal income tax to withhold for you.

Form W-4 includes worksheets to help you determine the number of withholding allowances you can claim. These worksheets are for your purposes only – do not give them to your employer.

What Happens If You Don’t Withhold Enough Tax?If you have too much tax withheld from your pay during the year, you will receive the overpayment as a tax refund after you file your return. But if you withhold too little, you may have to make Estimated Tax payments or be subject to an underpayment penalty.

Estimated Tax
If you don’t have any tax withheld from your pay (or you don’t pay enough tax through withholding), you may be required to pay estimated tax. Generally, estimated tax must be paid quarterly in 4 equal installments. For more information, see: What Is Estimated Tax & Who Does It Apply To?
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Underpayment Penalty
If you don’t pay enough tax, either through withholding or estimated tax payments, you may be subject to a penalty for underpayment. According to the IRS, you could owe a penalty if your total payments (from withholding and estimated tax) do not equal at least 90% of your tax liability for the year, or 100% of your prior year tax, whichever is less.