- You might underpay your taxes if you fail to file a second W-2 form. The income you reported on your return is missing the earnings from your second job, lowering your calculated income tax. You're still liable for the taxes you failed to pay. The IRS has the second W-2 on file and compares your return to the information reported by your employers. Once the agency notices you failed to file a second W-2, your return is automatically amended and you receive a bill from the IRS if you owe more money.
- Some tax credits, such as the earned income credit, are based on the amount of money you earned, so not reporting your second income might lower your credit amount. The IRS does not take additional benefits you might be entitled to because of the second W-2 when correcting your return for you.
Tax deductions are available for items such as contributions to a retirement account, so failing to report contributions you made on your second job might lower your deductions. - The IRS charges interest and penalties on the difference between what you paid in taxes and what you should have paid with the second W-2 added. The failure-to-pay penalty is 0.5 percent of the unpaid tax amount at the time of publication, up to a maximum of 25 percent of what you owe. The IRS charges the penalty each month from the time your return was due until you pay or the maximum is reached. You also owe the IRS interest on the unpaid taxes at the rate of the current federal short-term rate plus 3 percent.
- You can amend your tax return once you realize you've forgotten your second W-2 if the IRS hasn't already corrected it. Form 1040X is the form for amending most federal tax returns. You use the form to enter the additional information from the second W-2 and attach the W-2 to the amended form before sending the documents to the IRS. You can also use Form 1040X to add or change tax credits and deductions you took based on new information.