If your 19 year old is not a full-time student and has more than $4500 of her own income, you cannot claim her as a dependent. The 17 year old can still be claimed, but you will not get the child tax credit--he is too old. You will get the $500 credit for other dependents for claiming him.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
https://ttlc.intuit.com/questions/3113432-who-can-i-claim-as-my-dependent
For the 17 year old:
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:
https://apps.irs.gov/app/freeFile/
**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.**
