Your Short-Term Rental Tax Deductions Could Be at Risk: Here's What One Tax Court Case Reveals

A Tax Court decision should be required reading for anyone using short-term rental losses to offset their W-2 or business income. In Mirch v. Commissioner, T.C. Memo. 2025-128, the court denied a couple's rental loss deductions — not because their tax strategy was wrong in theory, but because they couldn't prove they did the work.

The case is a reminder that the IRS and the Tax Court care far less about your tax position on paper and far more about the documentation behind it.

The Setup: Two Attorneys, Two Rental Properties, One Big Tax Bill

The taxpayers in Mirch were a married couple — both attorneys — who ran a law firm in Reno, Nevada. One spouse even held an LL.M. in taxation and was a CPA. In other words, these were not unsophisticated filers.

They owned a vacation rental property next door to their home and rented it out on a short-term basis, with an average stay of fewer than seven days. For tax year 2006, they reported a loss of roughly $32,500 on the property and treated it as a nonpassive loss, using it to offset their law firm income.

The IRS disagreed. An audit followed, the taxpayers missed the deadline to petition the Tax Court after the Notice of Deficiency was issued, and the case eventually reached the court through a collection due process hearing. The court reviewed the underlying liability from scratch.

Why the Strategy Should Have Worked

The taxpayers' approach was grounded in a legitimate provision of the tax code. Under the passive activity loss rules of IRC § 469, rental activities are generally treated as passive — meaning losses can only offset passive income, not wages or business earnings.

However, there is an important exception for short-term rentals. If the average period of customer use is seven days or fewer, the property is excluded from the definition of a "rental activity." It is instead treated like any other trade or business. If the taxpayer materially participates in that business, the losses become nonpassive and can be used to offset ordinary income.

The Tax Court agreed that the Reno property qualified as a short-term rental. That part of the analysis went in the taxpayers' favor.

The problem was what came next: proving material participation.

Where It All Fell Apart — The Activity Log

To establish material participation, taxpayers must satisfy at least one of seven tests in the Treasury regulations. The most accessible test for many short-term rental owners requires more than 100 hours of participation during the year, with no other individual participating more.

The taxpayers submitted an undated summary log claiming the wife spent approximately 945 hours on the rental activity. The hours were broken down into three categories:

Emails (7.4 hours): The log allocated 12 minutes per email sent or received. The court found this reasonable and accepted it.

Cleaning (168 hours): The log claimed 7 hours of cleaning after each of the 23 rental stays. The court was skeptical. The taxpayers had also deducted nearly $10,000 in professional cleaning fees and charged guests a separate cleaning fee — economic evidence suggesting someone else was doing the cleaning. Making matters worse, the same 7-hour figure was assigned regardless of whether the stay lasted one night or two weeks.

Site Management (744 hours): This was the fatal category. The log assigned 8 hours per day for every day the property was rented, defined as being "on call for guests, repairs, supplies, Wi-Fi, cable, snow removal." This single line item accounted for roughly 80% of all claimed hours.

The court rejected it outright. Simply being available or on call does not count as material participation. The regulations require actual work — identifiable tasks with approximate time spent performing them. The taxpayers offered no calendar entries, no task-specific records, and no credible testimony about what the wife actually did on any given rental day.

The court characterized the entire log as a post-event estimate — what it called a "ballpark guesstimate" — and declined to credit it.

The Ripple Effect: No NOL Carryback Either

The consequences extended beyond 2006. The taxpayers had attempted to carry back a 2007 net operating loss to 2006 to further reduce their tax bill. But under the NOL rules, a loss must be carried to the earliest available year first — in this case, 2005.

Because the court also reclassified the rental losses for 2005 and 2007 as passive (based on the same documentation failures), the taxpayers' 2005 taxable income was higher than originally reported. The 2007 NOL was fully absorbed by 2005, leaving nothing to carry forward to 2006.

A documentation failure in one year created a cascading problem across three.

A Procedural Warning: Your Typo Could Validate the IRS's Actions

The case also included a procedural issue worth noting. The taxpayers challenged the IRS's filing of a Notice of Federal Tax Lien, arguing they never received proper notice. It turned out the IRS had mailed the notice to "3729 Jennings Street" instead of the correct "3728."

However, the taxpayers themselves had listed "3729" on their most recently filed tax return — a simple typo. The court held that the IRS was entitled to rely on the address shown on the taxpayer's last filed return as the "last known address," even if incorrect. The lien filing was upheld.

The Takeaways for High-Income Earners

The Mirch decision doesn't mean short-term rental deductions are off limits. The tax strategy itself is sound. What it means is that the IRS and the courts will not accept vague, after-the-fact estimates as proof of material participation.

If you're relying on short-term rental losses to reduce your overall tax liability, keep the following in mind:

Track your hours in real time. Maintain a contemporaneous log — ideally a digital calendar, spreadsheet, or property management app — that records the specific tasks you performed and when you performed them. A summary created at year-end or during an audit is almost always going to be challenged.

Be specific about what you did. Entries like "property management — 8 hours" are not sufficient. Record the actual task: responding to a guest inquiry, coordinating a plumber, restocking supplies, handling a check-in. The more granular, the better.

On-call time does not count. Being available to respond to issues is not participation. Only time actually spent performing services counts toward the material participation tests.

Standardized time blocks raise red flags. Assigning the same number of hours to every cleaning or every rental day signals that the log was reverse-engineered to reach a target rather than based on actual time spent. Real work takes irregular amounts of time.

Don't undermine your own position with your deductions. If you're claiming hundreds of hours cleaning a property while also deducting thousands in professional cleaning fees, expect the IRS to notice the inconsistency.

Double-check your tax returns — including your address. A simple typographical error gave the IRS a valid defense for mailing notices to the wrong address. Review every line before filing.

The Bottom Line

Short-term rental properties remain one of the most powerful tax planning tools available to high-income earners. The ability to generate nonpassive losses through depreciation and operating expenses can meaningfully reduce your overall tax burden. But the deduction only works if you can prove you earned it.

Mirch v. Commissioner is a case where the taxpayers had the right idea and the wrong documentation. Don't make the same mistake.