Feature lists for invoice approval systems have converged, and comparing them on capability produces a tie. The differences that matter operationally are three behaviours, all of which appear in the configuration rather than the brochure, and all of which determine how much elapsed time you actually remove after implementation.
Delegation during absence
What happens when an approver is on leave and has not set a delegate. Systems that require the approver to have thought about it in advance fail exactly when it matters. Automatic cover based on declared absence, or a fallback after a fixed period, is the difference between a predictable process and one with a long unpredictable tail.
Escalation that goes somewhere
After a defined period, does the item move to a named alternative, or does the system simply send another reminder to the same silent inbox. Reminders that repeat achieve very little; escalation with a deadline is what makes elapsed time a number you can promise a supplier. Ask specifically how escalation is configured and who it reaches.
What the approver actually sees
The document, the amount, the supplier, what it is for and the match result, or a reference and a total. This determines whether approval is a control or a formality, and it is easy to overlook because a demonstration always uses a clear example. Ask to see the approval screen with a messy real invoice.
Questions people ask about invoice approval systems
Does mobile approval matter?
For organisations where approvers are frequently away from desks, it is usually the largest single reduction in elapsed time available.
Should approvals expire?
Escalating rather than expiring is generally better, since an expired approval request usually just means somebody has to notice and resend it.
How do we test these three things?
In a trial, set an approver, then do nothing for the escalation period, and watch what the system does. That single experiment is more informative than any demonstration.