Do I need to estimate my tax liability to file an extension?

The short answer is only if you're planning to make a payment along with your extension BUT remember that an extension gives you more time to FILE your tax return, but it does not give you more time to PAY any taxes you owe. If you do not pay at least 90% of your tax liability by the original tax return deadline, you may be subject to late payment penalties and interest on the balance due.

If you're unsure, you should provide an estimate of the total tax you owe based on your best estimate of your income, deductions, and credits. Past history is always a good gauge. Do I usually get a refund or do I end up paying when I file my return? To estimate your taxes dues, you can use the tax calculator we provide or you can also use prior year tax returns to help you calculate your estimated tax liability.

It's important to keep in mind that an extension only applies to the filing deadline, not the payment deadline. So, if you owe taxes, you should try to pay as much as you can by the original tax deadline to minimize penalties and interest.