Why does my taxable income go up even though my 2 out of 5 property ownership/use years exclusion should more than cover the gain in a property sale?

[adrianfrankfurte]

I meet the qualifications of a partial exclusion - 23 months as a primary residence out of 4 years, 3 months ownership. I have a gain of approximately $100,000. Yet, my taxable income increased by $15,000.

[AmeliesUncle]

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@adrianfrankfurte wrote:
 23 months as a primary residence out of 4 years, 3 months ownership.

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What was going on during the other time it was not your primary residence?

Was it your primary residence AFTER it was used as something else?  Or did it start as your primary residence, then you used it for something else?

It was your main home for less than 2 years.  Which factor qualifies you for the exclusion when it was less than 2 years?