two options
1) include the interest on your return using form 8814
can only be done if his only income is interest, dividends and/or capital gain distributions (from mutual funds or ETFs)
he's under 19 or under 24 if a full-time student at the end of 2023
he can't file a return if married
2) file his own return and if under 24 at year-end use form 8615 to compute his income tax. form 8615 requires information from the parents' return.
if you're using online he needs his own account with a user ID and password. you can use your e-mail address
he cannot use your account because only one return can exist at any one time. Doing a second person's return will permanently delete the first person's return that is done
