With this feature you can enable Optix to create an invoice that is due today for additional charges from your users. We call this right-now-invoicing.
Example
A user has a plan that gives them 10 hours of room bookings and they have gone over their allowance today by 2 hours. With this feature turned on, that user will receive an invoice that is due today for the additional 2 hours at the rooms standard rate (minus any plan discounts).
Enabling "right-now-invoicing"
From your Optix web dashboard click Settings
Click Invoicing (you will need to have your payment gateway enabled to see these options)
From this screen you will see a drop-down section for 'Apply any additional charges' (see the screenshot below)
Select On a new invoice, due today

Recommend Settings
To fully realize the benefit of this feature it is advantageous to require users to enter a credit card when they sign up, you can enable this on the same Invoicing settings screen with the toggle next to 'Require users to add a payment method' (see the screenshot above).
Need more info on Invoices?