The $1,000,000 sale will put you in the 39.6% tax bracket, therefore, the tax on the capital gains amount will be 20%. SEE BELOW:
Report most sales and other capital transactions and calculate capital gain or loss on Form 8949 (PDF), Sales and Other Dispositions of Capital Assets, then summarize capital gains and deductible capital losses on Form 1040, Schedule D (PDF), Capital Gains and Losses. If you have a net capital gain, a lower tax rate may apply to the gain than the tax rate that applies to your ordinary income. The term "net capital gain" means the amount by which your net long-term capital gain for the year is more than your net short-term capital loss for the year. The term "net long-term capital gain" means long-term capital gains reduced by long-term capital losses including any unused long-term capital loss carried over from previous years. The tax rate on most net capital gain is no higher than 15% for most taxpayers. Some or all net capital gain may be taxed at 0% if you are in the 10% or 15% ordinary income tax brackets. However, a 20% tax rate on net capital gain applies to the extent that a taxpayer’s taxable income exceeds the thresholds set for the 39.6% ordinary tax rate ($413,200 for single; $464,850 for married filing jointly or qualifying widow(er); $439,000 for head of household, and $232,425 for married filing separately).
Now, in order to determine the actual amount of the gain, you must first determine the cost basis of the office and deduct the cost basis from the selling price. The remaining amount is the amount that capital gains tax will apply to, so without knowing any of that, I am unable to provide you with a definitive amount.
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