Yes, he does need to file a tax return, if the 4-H youth project payment was in his own name and he "cashed" the check so to speak.
In other words, he's clearly over the minimum income filing limit (threshold). This is true whether he is being claimed as a dependent on your own tax return, or if he is using his own personal exemption just as though he were an adult.
To verify these threshold amounts for yourself, please refer to the following (2) TurboTax FAQ pages below. (Click on the see entire answer button if the full pages are not readily apparent.)
Finally, as a money saving tip: if you plan to file multiple tax returns for a single household this year, you may be better off with the desktop software than with TurboTax online. The reason is that you can prepare multiple tax returns through the same program, rather than paying for each return one-by-one in TurboTax online.
We wish your son continued good fortune with the 4-H!
https://ttlc.intuit.com/replies/3302274
https://ttlc.intuit.com/replies/3302185
[Updated 01-16-2017]
SuperUser macuser22 makes some excellent additional observations, inasmuchas this question pertains to 4-H income. Thanks for the input!
