Your gross income, which includes the $30,000 capital gain, did not exceed the upper limit of $75,300 (assuming you are filing MFJ), therefore you will not be taxed on the capital gain. The Qualified Dividends and Capital Gain Tax Worksheet will be included in your forms for 2017. It is complicated but you can follow along the calculation there. After, $75,300 limit is met, you will be taxed at !5% on long term capital gains.