Use the Estimate Projects form to enter an estimate project header record.
You cannot invoice an estimate project. The fields on the Invoicing tab exist so you can create an estimate and then copy it over to the Projects form using the Copy Projects activity.
The fields on these tabs are not populated with data because you can not post transactions for an Estimate Project. These tabs are part of Estimate Projects to remain consistent with the Projects form. For information about the fields on this tab, see the similar fields on the Projects form.