What is the assigned identification number for someone incarcerated

[SabrinaD2]

Incarcerated individuals use their Social Security Number (SSN) or Individual Taxpayer Identification Number (ITIN) for tax purposes. 

The IRS does not generally issue a special tax identification number specifically for inmates

For more detailed information, you can refer to the following IRS resources:

• Individual Taxpayer Identification Number (ITIN)
• Prisoner Re-entry Program
• SSN Changes

If you need something else reach back out.

[xmasbaby0]

You do not mention why you are asking for an ID for a prisoner.   You will not be able to claim someone who is incarcerated as a dependent.   Their support is being provided by the corrections facility they are in; any money you are providing for incidental expenses, etc. is a gift, which is not deductible.