I’m 22 in the first year of my PhD
Do you qualify to be claimed as a dependent on your parent's tax return? If yes, then that does not necessarily mean it's taxed at the highest tax rate. It just means it's taxed at your parent's tax rate. But for a stipend which is basically for everything but education expenses, I'm not even sure about that. Even though a stipend can most certainly include qualified education expenses. A stipend is basically treated the same as a grant.
