how do I turn the input taxed function on not in GST drop down box.

Hi there, 

If your QuickBooks Online account is under the Simple GST/BAS function to classify and code GST in your transactions. You are no longer required to use the Input Tax tax code. To check your GST set up, I recommend contacting our Customer Care Team. That way, they can determine if your account is under Simpler BAS or Detailed BAS setup.

To learn more about GST set up, you can check these links  below:

• Simpler GST FAQ
• Switched to Detailed GST

Drop by again in the Community if you have other questions about GST.