How do I complete the extension form?
Enter the total tax liability you expect to report on your return. Make your estimate as accurate as you can with the information you have. If the IRS later finds that the estimate wasn’t reasonable, the extension may be null and void.
Amounts previously paid for current tax year
Do not include any amount you plan to pay with your extension. Enter the total payments you paid through quarterly estimated payments and tax refunds applied to the current year.
Amount Paid with Extension
Enter the total amount that you plan to pay with your extension. Your "Tax Liability" minus your "Tax Payments" would be the total "Balance Due" on your return. You can choose to pay that amount in full, in part, or you can choose not to pay any amount with your extension. If you do not pay the amount in full, you will owe interest on any amounts not paid by the mid-April deadline, plus a late payment penalty if you have paid less than 90 percent of your total tax by that date.
If you plan on making a payment with your extension, select Go to Extension Payment. Otherwise, click Continue.
What amounts should I enter?
All amounts that you enter on your Form 4868 should be the close to the amounts that you expect to report on your return. They do not have to be the exact calculations, but they should be relatively accurate estimates.
Filing the extension
Extensions must be filed by the original due date of the return. Most tax years that is April 15th. For the 2020 filing year, the date was extended to May 15th due to the distribution of stimulus payments that were required to be reported on the tax return.
You can e-file the extension in the program or file the extension by mail (postmarked by the original filing deadline).