Most accounts payable workflow diagrams show the clean path: invoice in, matched, approved, paid. Real workflows spend most of their effort on the branches off that path, and the branches are usually undesigned, which is why invoices go missing. There are three of them, they are predictable, and naming them turns an informal process into one you can measure and staff.
The clean path
An invoice arrives quoting a purchase order. It is captured, matched against the order and the goods receipt within tolerance, routed to the approver named by the rule for that cost centre and value, approved, coded and scheduled for payment on terms. Nothing about this path is difficult, and in a healthy process it is where most invoices go. The share that takes it is the single best measure of how well the upstream is working.
Branch one: no order, so no match
The invoice references nothing. Somebody must establish what it is for and who authorised it, which is research rather than checking. This branch needs an owner and a target, otherwise it becomes the queue everybody hopes somebody else is working. It is also the branch to attack at source, because every invoice here is a purchasing behaviour rather than a payables problem.
Branches two and three: mismatch, and query
A mismatch is a difference outside tolerance on price or quantity, and it should route by the reason to whoever can resolve it: purchasing for price, the receiving site for quantity. A query is anything else, most often a supplier disputing something or a duplicate. Both need an age and an owner. An exception with neither is not in a workflow at all, it is in a pile.
Questions people ask about accounts payable workflow
What share of invoices should take the clean path?
It is bounded by your purchase-order coverage, so measure that first. Chasing a published benchmark without knowing your own coverage tells you nothing about whether your process is healthy.
Who should own the exception branches?
Somebody named, with an ageing target. The commonest failure is a shared mailbox that everybody can see and nobody owns, where items age quietly until a supplier calls.
Should approvals happen before or after coding?
Either works as long as it is consistent. What matters more is that the approver sees the amount, the supplier and what it is for, rather than approving a reference number in isolation.