Every invoice workflow has the same spine, so drawing it explains very little. What differs between an organisation that copes and one that does not is the design of the branches: the invoices with no order, the price and quantity mismatches, and the queries. Those carry most of the effort and most of the delay.
The spine
Received and identified. Validated against duplicates and known suppliers. Matched against the order and the receipt within tolerance. Routed for approval by cost centre and value. Coded, scheduled and paid with a remittance advice. In a healthy process most invoices take this route with almost no individual attention paid to them.
The four branches
No purchase order, which needs a fuller approval by whoever owns the spend. Price outside tolerance, which belongs to purchasing. Quantity outside tolerance or a missing receipt, which belongs to whoever takes deliveries. And query, dispute or suspected duplicate, which needs a named owner with the supplier contact.
What each branch needs
A reason recorded, an owner who is a person rather than a team, an age, and a target elapsed time. With those four, an exception is a short specific conversation. Without them it is a research task in a shared queue, and research tasks accumulate because everybody starts them and nobody finishes them promptly.
And the ability to move backwards
An approved invoice can turn out to be a duplicate. A matched one can be disputed. A workflow modelled as a strict sequence has nowhere to put those, so they leave the system and continue by email, where nothing records them. Permitting and logging backwards transitions keeps the history intact.
Questions people ask about invoice workflow
How many branches should there be?
Enough that each has a distinct owner and a distinct next action. Six or seven covers nearly everything; more usually means two reasons nobody actually distinguishes.
What should be reported?
Counts by branch and the age of the oldest item in each. Two small tables that fit on a page and tell a manager where to spend attention.
Where do credit notes belong?
Their own short branch, because they reverse an obligation rather than creating one and are mishandled by processes built only for invoices.