As an Admin, you can choose to activate the invoice checkbox. Users will then see and have the option to check the invoice checkbox when creating an expense, as you can see in the image below.
How to configure this as an Admin:
1. Go to Admin settings.
2. Go to Advanced settings page.
3. Check or uncheck the right checkbox and don't forget to save.
- Checked: the invoice checkbox is shown in all expenses
- Unchecked: the invoice checkbox is not shown