Q: real estate profit on primary house - unused portion taxed if not spent completely on new house?

A: Based on the information provided, it seems you are asking about the tax implications of selling your primary residence and using the proceeds to build a new home. Here are the key points to consider:

1. Capital gains exclusion: If you owned and lived in the home as your primary residence for at least two of the five years before the sale, you can exclude up to $250,000 of the gain from your income (or up to $500,000 if you're married and filing jointly).

2. Unused portion of the proceeds: There is no requirement to reinvest the proceeds from the sale of your primary residence into a new home. You can use the money however you choose without triggering additional taxes, as long as the gain is within the exclusion limits mentioned above.

3. Building a new home: The cost of building your new home does not directly impact the tax treatment of the gain from the sale of your previous primary residence. The capital gains exclusion applies regardless of how you use the proceeds.

4. State tax considerations: While the capital gains exclusion is a federal tax provision, it's essential to consider any state-specific tax rules in Kansas and Nebraska that might apply to your situation.

In summary, based on the information provided, you likely won't be taxed on the unused portion of the proceeds from the sale of your primary residence, as long as the gain is within the $250,000 exclusion limit (assuming you meet the ownership and use requirements). However, it's always best to consult with a qualified tax professional who can evaluate your specific circumstances and provide personalized advice.