Get your taxes done using TurboTax

Yes, you can prepare and file taxes, using TurboTax, for your incarcerated brother since you have his permission.  However, he would be responsible for the return outcome. Source: DMarkM1

To check if he need to file a tax return, see Do I need to file a federal return this year?

If he is eligible for the stimulus payments and needs to file a tax return to claim the Recovery Rebate Credit, see How do I claim the Recovery Rebate Credit in TurboTax?  Please see the stimulus eligibility requirements below.

To be eligible for the first stimulus payment: Generally, if you are a U.S. citizen or U.S. resident alien, you will receive an Economic Impact Payment of $1,200  ($2,400  for a joint return) if you (and your spouse if filing a joint return)  are not a dependent of another taxpayer and have a Social Security number valid for employment and your adjusted gross income (AGI) does not exceed:

• $150,000  if married and filing a joint return
• $112,500 if filing as  head of household or
• $75,000  for eligible individuals using any other filing status
  Your payment will be reduced by 5% of  the amount by which your AGI exceeds the applicable threshold above.

You are not eligible for a payment if any of the following apply to you:

• You may be claimed as a dependent on another taxpayer’s return (for example, a child or student who may be claimed on a parent’s return or a dependent parent who may be claimed on an adult child’s return).
• You do not have a Social Security number that is valid for employment.
• You are a nonresident alien.
  The following are also not eligible: a deceased individual or an estate or trust.

To be eligible for the second stimulus payment, your adjusted gross income (AGI) is below,

• $75,000 for individuals
• $112,500 for heads of household
• $150,000 for married, joint filers

You should receive $600 per individual plus $600 per qualifying child.

For filers with income above those amounts, the payment amount is reduced by $5 for each $100 above the $75,000/$112,500/$150,000 thresholds. This means:

• An individual without children will not receive any payment if their AGI exceeds $87,000
• A couple without children will not receive any payment if their AGI exceeds $174,000
• A family of four will not receive any payment if their AGI exceeds $198,000

You can find your 2019 AGI on line 8b of your Form 1040.

 To be eligible for the third stimulus, you need to meet the following requirements: 

• Families earning less than $150,000 a year and individuals earning less than $75,000 a year should get the full $1,400 per person.
• Families earning up to $160,000 per year and individuals earning up to $80,000 per year will receive prorated amounts.
• One notable difference from the first two stimulus is that you will receive stimulus payments for all your dependents, including adult dependents and college students.