@billcsho you’re wrong. I literally just filled out my taxes and this is my third year filling out taxes as a graduate student- sometimes with fellowship and sometimes with a GSI salary. Our stipend is reported on our 1098T form. Box 5 is our tuition waiver + stipend amount and box 2 is our billable fees. Box 5 - Box 2 = our stipend (plus any other funding you get that isn’t part of a hourly or salaried job… like research and travel grants). THAT is taxable but you have to file your own taxes because it’s a stipend and treated like a scholarship.
SALARIES such as you get from a GSI/GSRA postion have taxes taken out with each paycheck.
There is a difference between a fellowship stipend and a teaching salary.
Perhaps things have changed since you were in school?