The IRS does not require you to enter an ID to file a tax return. Some states require a driver's license or state ID in order to e-file; if he does not have one, then his state return could be filed by mail instead of e-filing it. But it needs an signature in ink---either his own signature or the signature of a person who hold POA.
If you are trying to file a 2023 return, it is too late to e-file it. E-filing for 2023 closed at the end of October. The only way to file a 2023 return is by mail. If you are talking about his 2024 return, you have until mid-April to sort out the POA issue, or even longer if he gets an extension.
If he is getting a refund or does not owe, there is no penalty for filing after the deadline. If he owes tax due, he is subject to late filing penalties and interest for 2023, and would need to pay his 2024 tax due by the April 2025 deadline.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
