You can restrict who can and can't invoice your customers by setting up their user account with the Invoicing Permission. You can do this by defining permissions for a Role, and then assigning that Role to a User.
Follow along with this tutorial to see how it's done.
Step by Step:
First of all, go to your My Company settings.
Scroll down to the Roles section on the My Company page and click on the role for which you want to edit permissions.
This generates a popup. Turn the toggle on or off to show or hide pricing information and hit Save.
Next, go to Users on the main menu and select the User whose permissions you wish to edit.
Turn on the toggle for the role which you want the user to have, with the desired permissions.
If you have any questions, drop us a message in the blue chatbox.