Is There a Penalty for Filing a Tax Extension?
For most individual taxpayers, there is no separate IRS penalty just for requesting a valid filing extension, as long as you properly submit the extension request by the original due date of the return. However, an extension to file is not an extension to pay. Interest accrues on unpaid tax from the original due date, even if an extension is filed. If you do not pay enough of your tax by the original due date, you may owe late-payment penalties and interest on the unpaid balance. Depending on your situation, you may also owe estimated tax penalties if your withholding and estimated payments during the year were insufficient.
You are still required to file your return by the extended due date. If you miss the extended deadline, the IRS can impose late-filing penalties based on the tax that remains unpaid as of the original due date.
You should also consider any applicable state or local rules, because state extension, penalty, and interest rules can differ from the federal rules.
State Law Note
State extension, penalty, and interest rules are administered at the state level and can differ from the federal rules above. The controlling authority is the applicable state revenue department or tax agency.
Sources
IRS — Get an extension to file your tax return
IRS — Topic no. 304, Extensions of time to file your tax return