Order Dates and Unpaid Invoices

Hi all,

You might be able to help me solve a problem for our Education department. We do a lot of concerts in schools where we don't invoice until after the event, when the final attendee numbers came in. I have two questions:

Question 1:

We're interested in being able to create early orders with temporary numbers, which we then finalise later. But we run into a problem with the printed invoiced.

Currently, the date we use on our invoices is the Order Date. And that's the date that the school has 30 days to pay the invoice from. But if we create an order months before, the Order Date will be all wrong on the invoice. So I was wondering is there a way around this? 

I was thinking of using the Hold Until date (which isn't otherwise being used for these orders) because you can change that date later, but would that cause me problems that I don't know about?

Question 2:

We've normally used the On Invoice payment method, which marks the order as being Paid, and then creates an outstanding invoice amount. But I wanted to explore what would happen - given that we don't need to print tickets out for schools orders - if we just left an order unpaid and then just paid it off using Check or Credit Card or whatever payment method came through.

The question here is: would there be a way of distinguishing between an order that is in a temporary state and not finalised (like the ones I mentioned above) and one that has been finalised but not paid? Would that require some sort of custom flag on the order if I wanted to go down that path?

Hope this all makes sense. Look forward to hearing from other people out there.