If you are using TurboTax Online: 

1. Go to the Tax Home page, click on Deductions, and then click on Claims For Dependants. 
2. Answer YES & click Continue. 
3. Click on Enter Credit info next to the dependant whose info you want to change. 
4. Leave “Amount for an eligible dependant” checked off. 
5. Continue through the pages until you get to the Amount for an eligible dependant page.
6. Change your answer to No, and then click Continue to save.  
7. If you’d like, you can then you can go back to Step 3 & uncheck “Amount for an eligible dependant”.