A purchase order approval system encodes a policy the organisation already has, and most of the trouble comes from the gap between the written policy and what people actually do. Three details close that gap: thresholds the requester can see before they submit, automatic cover when an approver is away, and a rule for what happens when an approved order is later amended upward.
Visible thresholds
A requester who knows in advance that an order over a certain value needs a second signature plans for it. One who discovers it after submitting experiences the system as arbitrary and starts splitting orders to stay underneath, which is the behaviour thresholds exist to prevent. Showing the rule at the point of submission costs nothing and removes most of the friction.
Cover that happens without being asked
Absence is the largest single cause of approval delay, and manual delegation is forgotten precisely when it is needed. Automatic cover during declared leave, with escalation after a defined period regardless, is what makes elapsed time predictable. Escalation should go to a named alternative rather than to a reminder that repeats into the same silence.
Amendments, which are how limits get bypassed
An order approved at one value and later amended upward has effectively escaped its threshold. A rule that re-triggers approval above a percentage or an absolute increase closes that path. It is worth setting deliberately, because the alternative is discovering during an audit that orders routinely grew past their approved value one small amendment at a time.
Questions people ask about purchase order approval system
What thresholds should we use?
Whatever your existing delegated authority says. The system should enforce the policy rather than invent one, and if the policy is unclear, that is the thing to fix first.
Should the requester be able to approve their own order?
No. Separating the request from the approval is the point, and a system that permits it under any configuration is worth questioning.
How do we handle orders against a framework agreement?
Usually with a lighter approval, since the commercial terms were approved once when the agreement was signed. Make that an explicit rule rather than an informal practice.