With online TT, each user needs an account and a user ID. You can use the same email for up to five accounts, but your child needs his own account and user ID. He is too young to e-file. His return will have to be filed by mail.
MY DEPENDENT HAD A JOB
If your dependent has a W-2 for his after-school job, summer job, etc. you do not include the information on your own return. You can still claim your child as a dependent on your own return. He/she can file his own return for a refund of some of his withheld wages (he won’t get back anything for Social Security or Medicare), but MUST indicate on it that he can be claimed as a dependent on someone else’s return. (Supervise this closely or prepare it for him!)
If your dependent’s earnings were over $400 and were reported on a 1099Misc or 1099NEC then he must file a return and pay self-employment tax for Social Security and Medicare.
You might also want to use free software from the IRS Free File versions:
The TurboTax online editions are only available for one tax return per User ID. If you are going to use the Online editions for your daughter you will have to create a new account with a new User ID. You can use the same email address for up to 5 Online accounts.
Note - since she is under the age of 16 her tax return can only be printed and mailed to the IRS, it cannot be e-filed.