If your son is 19 and a full-time student you COULD claim him as a dependent. Why did you think you could not? You lost the child tax credit when he turned 17, but you could still claim him as a dependent and get the personal exemption for him and possibly EIC if you qualified. Examine your tax returns from those years--did you enter him as a dependent? Look on line 26 of your 1040A or line 42 of your 1040 to see how many exemptions you claimed. If you did not claim your son as a dependent on your past returns, you can amend to change that. Post back for further help with amending if you need help.
Since he is your dependent while in college (until he reaches his 24th birthday) you can be claiming the college expenses on your tax return, too.
A child of a taxpayer can still be a “Qualifying Child” (QC) dependent, regardless of his/her income, if:
1. He is under age 19, or under 24 if a full time student for at least 5 months of the year, or is totally & permanently disabled
2. He did not provide more than 1/2 his own support. Scholarships are considered third party support and not as support provided by the student.
3. He lived with the parent (including temporary absences such as away at school) for more than half the year
If you meet those three rules and TurboTax (TT) is not giving you’re the dependent, you are answering one or more of the interview questions wrong. Possibly the one about how long the child lived with you. A student away at college is considered to have lived with you all year.
If you are divorced from the other parent, the questions about which parent can claim the kid can be tricky.
My bet is, the reason you couldn't claim the student on your tax return in previous years, is because you didn't read the screen (as most do not) and therefore incorrectly indicated the student did not live with you for "the entire year". It's a common mistake that can be avoided by reading the information presented on that screen. The small print really does matter, big time.
IN the desktop version of TurboTax, the small print I'm referring to is on the screen "Tell us a bit more about [name]". It's the screen in the dependents section under the personal info tab where you select the number of months the dependent lived with you. That small print reads, "If your child was away at college, count the number of months away as having lived with you".
If you need to, you can amend your tax returns back to and including 2014 and get any additional refund you may be due, "PROVIDED" your dependent did not take any of the education tax credits or take the self-exemption on their tax return (if they filed one). Don't bother amending the 2013 return for additional refund. The 3-year grace period for that is past, and if you would be due a refund, you will not get it anyway.