Yes, a one time stipend is taxable.
However, if you are paid a stipend, it isn't considered wages so you won't pay Social Security or Medicare taxes on it. But, it still counts as taxable income for income tax purposes. Your employer won't withhold any income taxes from the stipend.
To report a stipend in TurboTax Deluxe
With TurboTax open select Federal taxes and then select Wages and Income.
Select I'll choose what I work on.
Scroll down to Less Common Income.
Select Miscellaneous Income.
Select Other reportable income, when asked Any other Taxable Income? click yes.
Enter your stipend amount and click continue.