This may be helpful
https://ttlc.intuit.com/community/after-you-file/discussion/can-i-file-someone-[product key removed]....
If you are using desktop, you can prepare and file up to 5 different returns.
Mechanically, to file the return, you will need SSN and specific driver's license number, the prior year's returns AGI (for security) and bank or credit card numbers for payment or refund.
This is how I did my parent's return. Now can you/should you not somewhere in the software that you are filing as their POA instead of them? Perhaps. I don't know how to do that. The 1040 form has a line for prepared by. I don't know how to fill that in with Turbo tax.
This says turbo tax only accommodates self prepared, so you woul d have to do it as described above, I assume
https://ttlc.intuit.com/community/taxes/discussion/where-to-input-my-name-if-i-helped-my-friend-prep...
