Question 3 of 35. To avoid a penalty for underpayment of estimated tax for 2021, a sole proprietor with an AGI below $150,000 ($75,000 if MFS) should make estimated payments in the amount of the smaller of % of the tax shown on their 2020 return or % of the tax shown on their 2021 return. 50%; 90% 90%, 50% 90%; 100% 100%; 90% Mark for follow up Question 4 of 35. If the taxpayer is not subject to phaseouts, the qualified business income deduction is the smaller of 20% of the qualified business income or 20% of the: Adjusted gross income. Net business income. O Taxable income