Idaho State Tax Commission

Valid Extension of Time

What you don't know about a "valid extension of time" for your individual income tax return can hurt you.

Top five extension misconceptions

An extension gives me extra time to pay my tax due

False. An extension is designed to give you extra time to file your tax return, not to pay your taxes.

A payment is never required if I received a refund last year

False. For an extension to be valid, you need to pay an estimated 80% of your current year's tax liability or 100% of what you paid for Idaho income taxes the prior year. However, sometimes the "100% of Idaho taxes paid last year" is assumed to be the bottom line from last year's tax return, but it actually refers to the "Total Tax" line. It's important to use the worksheet on Form 51, Estimated Payment of Idaho Income Tax, to help you calculate the correct amount.

There is no due date if I have a valid extension

False. If you have a valid extension you must file your return by Oct. 15. If you miss this deadline, penalty and interest will be charged.

Once you file your tax return, your extension expires and penalty and interest will be applied to any unpaid balance.

I need to send Form 51 to have a valid extension

False. You don't need to mail in Form 51 if you don't need to make a payment. Use the Form 51 worksheet area to determine how much your payment should be. If the "Payment due" line on Form 51 is zero or less, you just need to be sure to file your income tax return by Oct. 15 (or six months from your standard due date).

If I'm late, the penalty is the same whether or not I have a valid extension

False. Your penalty can be 5% of your tax due per month. (See the PENALTIES area under the General Information section of the Individual Income Tax forms and instructions packet.) Use our penalty and interest estimator to learn what you could be charged, or contact us if you have questions about how penalties are calculated.

Learn more on our Penalties and Interest page.

What to do if you don't have a valid extension

If it's after April 15, and you realize that you don't have a valid extension, the most important thing to do is file now and pay what you can — the entire tax due, if possible. This will greatly reduce the penalties and interest you owe — including penalties that can accrue at up to 5% per month from the standard due date.

Last updated May 23, 2014

This information is for general guidance only. Tax laws are complex and change regularly. We can't cover every circumstance in our guides. This guidance may not apply to your situation. Please contact us with any questions. We work to provide current and accurate information. But some information could have technical inaccuracies or typographical errors. If there's a conflict between current tax law and this information, current tax law will govern.