I don’t know of any other way to easily do these things right now beyond what you are doing. But you’ve brought up two distinct issues:
Invoicing billables. I and others have previously raised the difficulty of adding billable time or expenses to an existing invoice. This could be for the situation you describe, @jon, or it could just be that you’ve made a mistake in ticking boxes for items to be invoiced. It is very frustrating to delete and recreate an entire invoice because you forgot one billable hour or expense.
It was a big improvement when invoicing of billables was transferred to the Customers tab. At least now we can pick up both time and expenses. Before, you had to choose which module you would initiate the invoice from and manually add everything else. But I’ve always thought it was important to be able to select and add billables during editing, regardless of where or how the sales invoice is first generated.
Accounting for work in progress. Rigorous accrual accounting would have you recognize revenue as soon as the surrounding economic activity is substantially complete and the price can be determined with some degree of certainty. Completion of a fixed-price service, as you describe, definitely fits that bill. So such work in progress ought to be included in income even before it shows up by sales invoice in Accounts receivable.
My suggestion would be that such items be posted to a work in progress account just as billable time is now posted to Billable time - movement. In fact, they could both be posted to the same account, renamed as Work in progress. The question is where to input them. Do we need a separate Work in Progress tab? I don’t think so.
What if we had single module for Billable Services with the option of inputting time or fixed-price services? Entering a billable service would be equivalent to:
Dr Work in progress (asset account)–this is the current Billable time account
Cr Work in progress (income account)–this is currently Billable time - movement
Invoicing would then do the following:
Dr Accounts receivable
Cr Work in progress (asset)
Dr Work in progress (income)
Cr Service sales
There might be a little trickiness to rolling out the conversion because users might be allocating fixed price services to a separate income account right now than billable time services. How and whether to combine pre-existing accounts would need to be thought through.
Assuming this all works, there would be no need for a pre-invoice. And I think it would probably be much easier to implement.