I've recently started working at an events management company and am new with Sage as well.  

We organise conferences for our clients and start taking bookings for hotel rooms for groups many months in advance of the conference.  We currently invoice as soon as the group room booking comes in, and then proceed to produce a credit note and reinvoice each time there is a slight change in the room booking (adding or removing a person, changing the room type, etc).  

We send out the invoices and the customer is expected to pay in up to 4 installments.

I'm looking for a way to simplify this process.  We don't currently use the quote section of Sage 50, and I'm not sure this is the solution.  But what I would like is a way to accept deposits and post one correct final invoice just prior to the event.  

Any input would be much appreciated!