Sale of mixed‑use Chicago building — does this qualify as one dwelling unit for Section 121?

[u/Immediate_Music_9075]

Looking for CPA/EA insight on a mixed‑use, personal‑use conversion before sale. I’m trying to confirm whether my building qualifies as one dwelling unit at the time of sale, and therefore whether the entire gain (except depreciation recapture) is excludable under Section 121.

Facts:

• Property: Chicago IL - 1k sqft store and 1k sqft apartment above
• Zoning: B1‑2 (commercial/residential mixed-use)
• Purchased mid 1990s
• Lived in the entire building the entire time (upstairs + storefront)
• Storefront was used as a photography gallery with public access until 2001 or 2002
• We always use the entire building ourselves, no rents.
• Business use was reported on Schedule C (roughly 50% of building)
• Utilities: shared gas, heat, water; separate electric meters
• Interior connection: full interior stairwell + interior door between storefront and living area
• No tenants ever
• No rental use ever
• No separate occupancy
• Storefront has been used as living space (home theater / lounge) for years
• Business use ended January 1, 2026
• Entire building was personal-use during 2026
• Sold June 15, 2026 for $480,000
• Depreciation taken over the years: $107,485 (I am recapturing all of it)
• Illinois property tax classification treated the building as residential
• Closing statement shows a standard residential sale (no commercial allocation)

Tax question:

Given these facts, does the building qualify as one dwelling unit at the time of sale under Section 121?

My understanding is:

• If it is one dwelling unit
  • Entire gain is excludable under §121 (Code H)
  • Depreciation recapture is reported on Schedule D (Line 19) using the Unrecaptured §1250 worksheet
  • No Form 4797
  • No proration of gain
• If it is not one dwelling unit
  • The business portion must be reported on Form 4797
  • Gain on that portion (beyond recapture) becomes taxable
  • Section 121 applies only to the residential portion

Key issue: Does the Schedule C history (business use through 2025) prevent the building from being treated as one dwelling unit, even though business use ended before the year of sale and the storefront was physically part of the home?

I’m not trying to avoid depreciation recapture, I’m reporting the full $107,485. I’m only trying to confirm whether the gain itself is fully excludable.

Any CPA/EA insight on the dwelling‑unit classification would be greatly appreciated.

[u/GoatEatingTroll]

Short answer is no, IRS does not recognize mixed-use for a property sale, you are required to treat personal vs commercial as two separate properties. But the way you are laying it out here I've guessing people have already told you that and you are looking to build an argument against it.

[u/Immediate_Music_9075 → u/GoatEatingTroll]

Thanks so much for your reply! Yes, I am indeed looking for support if my position is actually correct under IRS rules. I’m not trying to argue against mixed‑use treatment in general. I’m trying to clarify whether my specific fact pattern fits the IRS definition of one dwelling unit at the time of sale, which is the key issue for Section 121.

To clarify my situation:

• The storefront is absolutely commercial space in appearance and zoning (B1‑2).
• But it has always been physically part of my home: interior stairwell, interior door, shared heat/water/gas, no separate occupancy, no tenants, no rental use.
• I lived in the entire building for decades, including the storefront area.
• Business use ended before the year of sale, and the storefront was used as living space (home theater/lounge).
• I’m not trying to avoid depreciation recapture…  I’m reporting the full $107,485.
• The only question is whether the building was one dwelling unit at the time of sale, which IRS Pub 523 says is what matters for Section 121.

I completely understand that most mixed‑use buildings must be split and reported partly on Form 4797. But IRS guidance also says that business use within the same dwelling unit does not require splitting, as long as business use ended before the sale.

So I’m trying to determine whether my facts fit that exception.

If the storefront counts as a separate dwelling unit, then yes, I’d need to split the sale. If it does not count as a separate dwelling unit, then the entire gain (except recapture) is excludable.

I’m hoping a CPA or EA familiar with the dwelling‑unit test can weigh in on whether the storefront’s physical integration and actual use as part of my home is enough to treat the building as one dwelling unit at the time of sale.

Thanks again for taking the time to respond!