Year-End Tax Reminders for Real Estate Investors: STR Stays, Cost Seg Timing, 1099s, and More

This Tax Smart REI Podcast episode is all about last-minute year-end clarity. Thomas Castelli and Nathan Sosa answer the flood of investor questions that always spikes in December, especially for people trying to make meaningful moves before December 31.

They cover the biggest “don’t mess this up” items: short-term rental requirements, placed-in-service rules, cost segregation timing myths, 401(k) and HSA deadlines, material participation logs, and 1099/W-9 compliance. Then they shift into rapid-fire Q&A from the Tax Smart investor community.

1) Critical Year-End Reminders for 2025

Major tax law changes to keep in mind

Nate flags that 2025 planning needs to reflect changes from the “One Big Beautiful Bill,” including:

• The return of 100% bonus depreciation
• Changes affecting SALT planning (they reference a “sweet spot” strategy conceptually)
• Expansion of Section 179 limits (helpful for some businesses)

(They keep this section high-level and focus the episode on practical, last-minute investor actions.)

2) Short-Term Rental Strategy: The Big Year-End Trap

Thomas gives one of the most important STR reminders investors miss:

You need guest stays in 2025

If you bought a short-term rental late in the year and want to use the STR strategy for 2025, you can’t just:

• close on the property, or
• list it online

You need real guest stays so you can calculate the average period of customer use for the year.

They also warn against “cute” workarounds that don’t hold up:

• Renting to friends/family at non-market terms
• Swapping stays (“you stay at mine, I’ll stay at yours”)

Don’t forget material participation + documentation

To treat the STR activity as non-passive, you need material participation and you need to document your time. They point investors back to prior episodes for the full breakdown but emphasize the kinds of work that generally count:

• Managing bookings and guest communications
• Pricing and calendar management
• Overseeing cleaning/turnovers (or doing it yourself)
• Repairs, maintenance, and getting the unit rent-ready

3) “Placed in Service” Requirements

Nate explains “placed in service” in plain terms:

For a normal rental, the property is typically placed in service when it’s ready and available to rent, the “someone could move in today” standard.

But for STRs, there’s a key extra layer:

You can be placed in service, but without guest stays, you may not be able to prove it qualifies as a short-term rental activity for the strategy.

4) Cost Seg Timing Myth: You Don’t Need It Done by December 31

Thomas reinforces a common misconception:

You don’t have to complete a cost segregation study by year-end to use it for 2025.

What matters is having the report ready for filing the 2025 tax return:

• Individuals: typically by April 15, or later with extension
• Entities: deadlines vary (they reference partnership/S-corp extension timelines)

So yes, don’t procrastinate, but also don’t panic. Rush a cost seg on December 29, thinking it’s required.

5) 401(k) and HSA Deadlines Investors Should Know

401(k) contributions

Thomas emphasizes the year-end timing for retirement plan contributions, especially employee deferrals.

Nate adds nuance:

• SECURE 2.0 created more flexibility for certain sole proprietors to set up plans later and still contribute for the prior year
• S-corps generally have less flexibility for setup timing
• Employee vs employer contributions have different rules and deadlines

HSA reminders

Thomas notes:

• The HSA needs to be opened by year-end
• Contributions can generally be made by the tax filing deadline (often April 15), even if you later extend your return

6) Audit-Proofing: Update Your Time Logs Before the Holidays

Nate gives a practical warning from Hall CPA’s audit defense experience:
Even if the audit isn’t “about” REP/STR, the IRS often asks for material participation logs when real estate is treated as active/non-passive.

And the best time to update logs is… now.

Because once you hit holidays, travel, and New Year’s, reconstructing time in January becomes guesswork.

They recommend:

• Keep logs current
• Be specific (not vague summaries)
• Don’t rely on travel time to “save” your hours (it’s often the first thing the IRS challenges)

7) Investor Q&A Highlights

Q: Can I combine hours for two STR units on the same lot?

Nate points to grouping rules (often referred to as the “dash four” grouping concept under passive activity rules), and explains the idea:
If structured correctly, you may be able to treat the two units as one economic activity so hours can be combined—helping you hit material participation thresholds.

Q: If I buy a vacation rental outside the U.S., can I still do cost seg and get the same benefits?

Thomas clarifies:

• You may still be able to use cost segregation and STR concepts, but foreign property is not eligible for bonus depreciation—which is often a major driver of the savings.

Q: How important are W-9s and 1099s?

Nate and Thomas are blunt: very important.

Best practice:

• Get a W-9 from every contractor you expect to pay $600+
• Get it before you pay them (because once paid, they may ghost you)

Why it matters:

• 1099s are due by January 31, 2026
• In audits, the IRS may ask you to prove you issued required 1099s
• Missing filings can create significant penalties

Q: Can travel time count toward REPS hours?

Nate’s framework:

• Track everything you think is legitimate, but try to hit targets without relying on travel time
• Travel is often the first thing challenged
• If travel is clearly tied to real work and supported (especially with a credible home office setup), some may be defensible, but it shouldn’t be the bulk of your hours

Q: Married filing separately—can one spouse’s REP/STR losses offset the other spouse’s income?

Nate explains that it depends heavily on state rules (community property vs non-community property) and facts.

High-level takeaway they land on:

• Filing separately can significantly limit how losses help the higher-earning spouse, so this needs careful planning before choosing MFS.

Q: REPS + long-term rental + STR + a long-term rental with a property manager: how does that work?

Thomas breaks down the planning concept:

• For long-term rentals, grouping elections can matter
• Property managers make material participation harder to prove on a given property
• STR hours can help with the 750-hour REPS test, but STR and long-term rental participation rules don’t always mix cleanly
• The practical “win” is structuring the long-term rental side so you can meet material participation thresholds in a defensible way

Q: Is this the last year for Qualified Opportunity Zone deferrals?

Nate discusses QOZ timing at a high level and frames it as a potential year-end deferral move if an investor has capital gains and wants to push recognition out—while noting newer rules may create additional planning angles depending on timing and structure.

If You Missed 2025, Get Ahead of 2026

They wrap with a realistic reminder:

If you’re not already positioned to execute a strategy cleanly for 2025, don’t force it at the last second.

Use the year-end checklist, and if you want to “come out of the gate running,” start planning early for 2026, especially with 100% bonus depreciation back in the mix

Disclaimer: This podcast summary was generated from the transcript and may contain some errors or miss key points from the audio recording.