There's important information on your W-2 that may not be on your final paystub. You should enter your W-2 to complete your tax returns because your employer is supposed to send copies to the IRS and state(s). If you enter amounts from your paystubs, your tax returns will not agree to the W-2 copies the IRS and state(s) received and they may contact you for more information. If you want to understand the differences, you should re-contact your employer because they issued your paystubs and W-2.