@2020brett You cannot have it both ways. In order for you to file as Head of Household you have to claim a qualified dependent. If your son cannot be claimed as a dependent you cannot file HOH unless you have some other blood-related dependent to claim.
And....since you claimed him, his return saying he cannot be claimed will be rejected when he tries to e-file.
Is he your dependent or not? You say he is 19. Was he a full-time student in 2021? If he was not a student did he earn more than $4300?
Am I Head of Household?
https://ttlc.intuit.com/questions/1894553-do-i-qualify-for-head-of-household
https://ttlc.intuit.com/questions/2900097-what-is-a-qualifying-person-for-head-of-household
If you qualify as Head of Household, when you enter your marital status (single or married filing separately) into MyInfo, and then enter your qualifying dependent, TurboTax will offer HOH as your filing status.
**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.**
