Married taxpayer who file a joint return and have taxable income of less that $340101 may be eligible to deduct 20% of their QBI. However, their deduction could be subject to a limitation based on:

Ordinary taxable income (before QBI) deduction minus net capital gains and qualified dividends.

Phase-in rules

Phaseout rules

The amount of their taxable income from Form 1040, line 15.