How to Figure a W2 Based Off Your Last Pay Stub

by Alia Nikolakopulos ; Updated September 11, 2015

While you wait for your W-2 to arrive in the mail from your employer, you may use your last pay stub to estimate the items reflected on your W-2. This allows you to get an idea of how much income tax you may owe when you file your tax return, or the size of your income tax refund. You may also use these steps to confirm entries on your W-2 once you receive it. If you note a discrepancy on your W-2 or believe an error was made, you may clarify your concerns with your employer prior to filing your tax return.

Obtain the Internal Revenue Service Form W-2 for reference. You may not use the W-2 to file your taxes, but you may look at the form to estimate your actual W-2 figures.

Figure your federal and state gross income. Locate your year-to-date (YTD) gross income on your last pay stub. Add any overtime or bonus compensation if the payments are listed separately from gross pay on your pay stub.

Subtract pretax deductions. If you elect no pretax deductions from your pay during the year, the YTD gross income, plus bonus and overtime payments on your pay stub equals your federal and state gross income. However, if you elect pretax deductions such as health insurance, 401k contribution or dependent care savings account deductions, subtract the YTD amount of the deductions from your YTD gross income. The result is your taxable gross wages for boxes 1 and 16 of Form W-2.

Figure your Social Security and Medicare taxable wages. Many times, your taxable wages for Social Security and Medicare is the same as the gross income amounts for boxes 1 of your W-2. However, some pre-tax deductions, such as 401k contributions are not exempt from Social Security and Medicare taxes. Add YTD 401k contributions, 403b annuity plan contributions or 457b retirement plan contributions to your box 1 gross income. The result is your Social Security Wages and Medicare Wages for boxes 3 and 5.

Look at the YTD taxes withheld on your paystub. You do not need to perform additional computations to figure your W-2 taxes withheld. The YTD federal income tax goes in box 2 of your W-2, the YTD state income tax goes in box 17, the YTD Social Security tax goes in box 4 and the YTD Medicare tax goes in box 6 of Form W-2.

About the Author

With a background in taxation and financial consulting, Alia Nikolakopulos has over a decade of experience resolving tax and finance issues. She is an IRS Enrolled Agent and has been a writer for these topics since 2010. Nikolakopulos is pursuing Bachelor of Science in accounting at the Metropolitan State University of Denver.