The Extension Trap: Why Filing a Tax Extension Might Be Your Smartest Move

If the words "tax extension" make you nervous, you're not alone. Many taxpayers assume filing an extension is a red flag, a sign of trouble, or even an invitation for an IRS audit. In this episode of Tax Talk Unfiltered, Spencer Carroll, CPA sat down with Rachel Richard, CPA from Gelt's product team to bust those myths and explain how an extension can actually be one of the smartest tools in your tax arsenal.

What Is a Tax Extension and What It Isn't

Filing a tax extension is exactly what it sounds like: an extension of time to file your return. What it is not is an extension of time to pay what you owe.

The IRS offers this because they understand not everyone has all their information ready by the April 15th deadline. Filing an extension gives you until October 15th to submit your return, penalty-free for the filing itself. But the IRS still expects you to pay your estimated tax liability by April 15th.

That means the extension only pauses the failure-to-file penalty. Failure-to-pay penalties and interest continue to accrue on any unpaid balance until it's paid in full.

Key takeaway: An extension is not more time to pay. It's more time to get your paperwork right.

Is Filing an Extension a Red Flag?

No, and this is one of the most persistent myths. Filing an extension does not trigger an audit and is not viewed negatively by the IRS. Millions of taxpayers file extensions every year, and the IRS built the system specifically to accommodate them.

Extension Deadlines to Know

Here's a quick reference for key extension deadlines:

• Individuals: April 15th (extended filing deadline: October 15th)
• S-Corporations & Partnerships: March 15th
• C-Corporations: April 15th
• Living outside the U.S. on April 15th? You get an automatic extra two months, until June 15th, to file your extension.
• State deadlines: These vary widely. Some states mirror the federal April 15th deadline, others run as late as May 15th, and some give you until November.

Safe Harbor and Estimated Payments

Safe harbor is a term most closely associated with estimated tax payments, not extensions, though the two frequently come up together. When you file your 2025 return during the extension period, you may simultaneously owe 2026 estimated payments. That creates a juggling act.

The IRS offers safe harbor protections for estimated payments, defined as the lower of:

• 100% (or 110%) of your prior year's tax liability, or
• 90% of your current year's tax liability

Because you may not have finalized your 2025 return yet, you might not know your exact safe harbor amount for 2026 estimates. This is where strategic payment planning comes in, applying payments in ways that provide a buffer against underpayment penalties even as the numbers shift.

One important distinction: for the extension payment itself, you're expected to pay 100% of what you owe, not a safe harbor amount. If you're uncertain about your final number, it's generally better to be conservative and slightly overpay rather than underpay and face penalties.

What Happens If You Don't File an Extension?

If you miss the deadline without filing an extension, here's what you're looking at:

• First offense in three years? You can request first-time abatement from the IRS. In most cases, they'll waive the penalties if you have a clean three-year history.
• Repeat situation? Every month your return goes unfiled, you'll owe a failure-to-file penalty. On top of that, a failure-to-pay penalty and interest accrue on any unpaid balance until it's fully paid.

One important note: even if you can't calculate your final liability, filing a zero extension is far better than filing nothing. And while you can't file an extension after the deadline has passed, you can continue making payments at any time. Each payment stops additional penalties and interest from accruing on that amount.

How to Use Your Extension Time Wisely

Filing an extension isn't permission to put your taxes on autopilot until October. Here's how to make the most of those six months:

1. Pull Your IRS Wage and Income Transcript

In mid-May, the IRS releases a transcript of all tax forms they received for you during 2025. You can download it online and compare it to your return to make sure everything the IRS has, you've reported. This can prevent automated notices from triggering down the road.

2. Maximize Deductions and Credits

Use the extra time to go through your books carefully, capture every legitimate business deduction, and gather documentation for any credits you qualify for. You're not competing for your CPA's time with hundreds of other April 15th filers. Use that focused attention to your advantage.

3. Make Retirement Contributions

Depending on the type of account, you may still have the opportunity to make retirement contributions for the 2025 tax year during the extension period. Business owners with SEP-IRAs or Solo 401(k)s often have until the extended October 15th deadline. Note: HSA contributions for 2025 must be made by April 15th. They don't get the extension benefit.

4. Complete a Cost Segregation Study

If you placed a piece of real estate in service in 2025 but haven't completed a cost segregation study yet, you can do the study in 2026 and still apply the accelerated depreciation benefits back to 2025. The key is that the property was placed in service during the tax year in question.

5. Consider Entity Structuring Opportunities

Here's one that surprises many people: if you have an LLC, you can potentially make an S-corp election retroactive to 2025, even now. Because 2025 is a closed year, your P&L is locked in, which means you know exactly what the benefit will be before committing to the election. You'd be filing late, but first-time abatement typically covers those penalties.

If you go this route, you'll need to handle reasonable W-2 compensation for 2025. Options include running a late payroll (subject to potential penalties, often waivable with first-time abatement) or treating the equivalent compensation as self-employment income via a 1099. The payroll route is generally preferred for establishing proper reasonable compensation.

Who Should File an Extension?

Almost anyone can benefit from an extension, but it's particularly valuable if you're:

• Waiting on K-1s or other information that won't be available by April 15th
• Dealing with variable or uncertain income, making it hard to accurately estimate your final liability
• A business owner exploring deductions, entity structuring, or retirement account contributions
• Someone who wants focused, unhurried time to ensure your return is fully optimized

Who Probably Doesn't Need One?

If your situation is straightforward and you're confident you're getting a refund, there's little reason to wait. The sooner you file, the sooner that money is back in your pocket. But for almost everyone else, the strategic value of the extra time far outweighs any reason to rush.

The Bottom Line

An extension is a tool the IRS gives you. Use it. It's free, it's easy, and it buys you time to make sure your return is right the first time, rather than filing hastily and needing to amend later (which can take the IRS up to 16 weeks to even process).

There are often tens of thousands of dollars in strategy opportunities still on the table during the extension period. Don't let the April 15th deadline make you feel like the window has closed, because in many ways, it's just opening.

If your current CPA isn't helping you think strategically about extensions and tax planning, you may be leaving real money behind. Even after April 15th, it's not too late to start.

This post is based on an episode of Tax Talk Unfiltered, Gelt's podcast featuring insights from our team of CPAs and tax professionals. Listen to the full episode for the complete conversation.