Match approvers to the spend band
Under £500: line manager only. £500–£5,000: line manager plus budget owner. £5,000–£25,000: add the project sponsor. Over £25,000: add finance and a director. Build the bands once and let routing handle them automatically. The reason this works is that the marginal value of an additional approver drops sharply with each level — once three competent people have reviewed a £2,000 spend, a fourth is not catching anything new and is just adding latency. Match the depth of scrutiny to the size of the risk, not the size of the form.
Distinguish budgeted vs unbudgeted
Budgeted spend within an approved project envelope deserves a lighter touch than unbudgeted spend. A second routing dimension — budgeted vs unbudgeted — halves approval cycle time on the bulk of requests and concentrates scrutiny where it matters. Many organisations run a single workflow that treats £500 of pre-approved consumables the same as £500 of unbudgeted entertainment. The risk profile is completely different, and the routing should reflect that.
SLAs make the system real
An approval chain without an SLA is just a queue. Set explicit response windows (e.g. 24h for under £5k, 48h for under £25k, 72h for over) and auto-escalate misses to the approver's manager. The SLA tells your team what 'fast' looks like and gives finance visibility of bottlenecks. Just as importantly, it tells the requester when to chase and when to wait — removing the constant 'has anyone seen my approval?' messages that clog every operations team's chat channel.
Out-of-office and delegation
Half of the approval delays in any organisation come from approvers being out of office and not delegating. Build out-of-office and named-delegate into the workflow itself, not into individual approvers' inboxes. When the approver flips their status, the system reroutes — no exceptions, no manual chasing, no requester following up by chat.
Spend categories with their own logic
Some spend categories deserve special routing. Software subscriptions need an IT or security review. Marketing spend over a threshold needs a brand review. Capital expenditure needs a finance and (sometimes) a board review. Build category routing alongside spend-band routing, and surface the additional approvers automatically when the category triggers them.
Reporting that drives design changes
The point of an approval workflow is not to approve things; it is to expose where the operation actually spends and where the friction lives. Monthly reporting on approval cycle time, denial rate by approver, and spend by category turns the workflow into a management tool. If a particular approver is denying 40% of requests, either the policy is wrong or the requesters are not informed — both are fixable, but only if you see the data.
When to redesign
Approval workflows accumulate complexity over time as people add 'just one more approver' for the last embarrassment. Schedule a review every 18 months: are the SLAs being hit, are the approvers adding value, are the bands still right for the size of the organisation? A periodic prune keeps the workflow proportionate to the risk it is managing.
Good approval design protects the operation from risk and from itself. Speed and control aren't trade-offs when the routing is right — they are two outputs of the same well-designed system.