The symptom
Tracking built on invoices looks at the past.
In most organizations, the financial tracking of a project comes from accounting: what was invoiced, what was paid, possibly what was provisioned. This is reliable, audited data, and systematically late.
The lag is mechanical. Production takes place, it is entered sometimes a week late, approved at the end of the month, invoiced the following month, paid thirty to sixty days later. When a gap appears in the accounting dashboard, it is between six weeks and three months old.
On a six-month project, that is half the project. Financial tracking built on issued invoices looks at the past. Financial tracking built on what the field has consumed looks at what is being done now.