Yes, you must file a tax return to get withholding refunded. Yes, check the box SOMEONE CAN CLAIM YOU AS A DEPENDENT on the first page of 1040 in your return.
With the tax law change, effective 2018, most student-dependents will get the same refund whether they claim themselves or not. The personal exemption has been eliminated and the standard deduction increased.
If a dependent has sufficient income (usually more than $12,200), he can & should still file taxes. In TurboTax, he indicates that somebody else can claim him as a dependent, at the personal information section. TT will check that box on form 1040.
Even if he had less, he is allowed to file if he needs to get back income tax withholding. He cannot get back social security or Medicare tax withholding.
