To add the supplement price of Double/Triple/Quadruple accommodation, please see the steps below.
Create a Menu Item 'Supplement'
In your Booking, create an Event called Supplement
Add the Menu Item 'Supplement' to the Event and set the Quantity and Price
Add Booking Item to Prepayment Invoice
For Users with Automatic Posting, ensure that the Revenue Category is not set to automatically post to MEWS.
For Users using Manual Posting, ensure this Menu Item is not posted to MEWS to avoid double charging.