If you want to prepare a tax return for your son, create an account for him---or sit with him while he does it himself.
When you use online TurboTax, each return needs its own account and user ID. So he needs an account and user ID, even if it is still under your email. Do not let him use your account or user ID or it will overwrite your own return and yours will be lost.
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-onli...
**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.**