@thinkatoz1
i’m afraid the previous answer is incomplete. The IRS requires form 2848, which is a special tax-only power of attorney form. If you are able to visit the incarcerated person or mail them a form and have them mail it back, they should fill out and sign part 1 of form 2848, which specifies exactly what authority you will have regarding their tax return. You complete and sign part 2 which is the statement of the representative.
If you cannot get the incarcerated person to sign part 1 of form 2848, you can file their tax return by including a copy of your power of attorney form, but you must also include form 2848 where you have signed the representative statement in part 2.
If you file by mail, you will sign the tax return with your name and then write POA and the taxpayers name next to it, but you will also include form 2848 and a copy of your POA if the taxpayer has not signed part one of form 2848. If you e-file, you must mail a copy of form 2848, a copy of the POA if required, and a form 8453, which is a cover sheet that is used when mailing documents to the IRS after e-filing.
https://www.irs.gov/pub/irs-pdf/f2848.pdf
https://www.irs.gov/pub/irs-pdf/f8453.pdf
