The Estimate function may work for some things but I have not found a way to make it work for Billable time and items. My situation is such that we do both Billable and non-billable invoicing. I need to create draft invoices that do not affect the aging reports so that the project managers can review/edit invoices and then I make the final changes. Once the final changes are approves, I remove the Pending flag and release the invoice to the customer. Not having the Pending status on the invoice affects our aging reports, so not having this status makes the software very bad for our business practices.