This is the information I found from the article, Should I Include a Dependent's Income on My Tax Return?

"For 2016, Dependents who are not 65 or older or blind, who have earned income more than $6,300, must file their own return. Income levels required to file a return for those 65 and over or blind are higher. You do not include their earned income on your taxes. If they earned less than $6,300 in 2016, they do not have to file a return, but may wish to do so to recover any withheld income taxes. You can still claim the dependent exemption, and the dependent will not be able to claim her personal exemption on her own return." 

https://turbotax.intuit.com/tax-tools/tax-tips/IRS-Tax-Return/Should-I-Include-a-Dependent-s-Income-...