Here are a couple of things you should know about the ‘New’ button in lookup window
- The button is visible only for ‘Account’ & ‘ Contact’ lookup relationship. It is not available for any other lookup relationship
- You can’t customize the layout that is displayed when you click on ‘New’ button from the lookup Window
- Account / Contact record created from the lookup window bypasses validation rules (i.e. validation rules are not enforced)
- Creating a ‘New’ contact from the lookup window does not associate it to any account (i.e. creates it as a private contact)
![New Button on Lookup Window](https://amazon.asagarwal.com/images/new_button_in_lookup_window.png)
It is probably be a good idea to hide this button from the lookup window. Navigate to Setup -> Customize -> User Interface and uncheck the option ‘Show Quick Create’
![Hide new button in lookup window](https://amazon.asagarwal.com/images/disable_new_button_in_lookup_window.png)