Invoice approval workflows that don't become bottlenecks

Slow invoice approvals cost more than late payment interest. They eat your team's time, strain supplier relationships, and put your payment terms at risk. Under the UK's Fair Payment Code, which replaced the Prompt Payment Code in December 2024, how you perform on payment terms is now scored publicly.

If most of your invoices need senior sign-off, or one absent approver can stall a payment run, the bottleneck is in the workflow design. The rest of this article looks at how to remove those bottlenecks and keep routine approvals moving.

Why approval delays are now a compliance and cost problem

The Fair Payment Code's Gold Award requires settling 95% of invoices within 30 days of receipt. If your internal routing alone takes 15 days, you've already used half your window before the payment run begins. A payment term measured from "after approval" doesn't meet that standard. It needs to fit inside the 30 days from the day the invoice lands.

UK late payment rules are backed by law. Under the Late Payment legislation, you owe statutory interest on any overdue payment, regardless of whether the cause was an absent approver, a misfiled invoice, or a three-way matching failure. HMRC's Making Tax Digital rules also require an unbroken digital trail from the moment you capture invoice data through to your VAT return. The approval workflow sits inside that chain.

The total cost is harder to see than any single delayed payment. Department for Business and Trade (DBT) late payments research found that 36% of businesses blame late payments on administrative errors like failing to log invoices, rather than deliberate stalling. Anyone who has spent a Friday afternoon hunting down a department head for a signature on a £3,000 invoice knows what that looks like up close.

How to design approval tiers that don't create queues

Most approval bottlenecks come down to one structural mistake. Too many invoices get routed to too few approvers. If your finance director personally signs off every invoice above £1,000, you've guaranteed a bottleneck every time they take annual leave, attend a board meeting, or just have a busy week. And finance picks up the slack. Five follow-up messages a day from colleagues asking "where are we with that invoice?" is how the team becomes the department that slows everything down.

The ICAEW finance toolkit points out that senior management often has a different picture of how processes work than the people running them day to day. For example, there's often no clear answer to who gives final approval on invoices, who chases the cash when a customer doesn't pay, or who owns the problem once an invoice goes into default.

The fix doesn't start in your AP software. It starts with a formal Delegation of Authority policy, a board-approved governance document that defines who approves what, and up to what value.

Setting thresholds that match your invoice volume distribution

Set your thresholds so that most invoices get approved at the lowest tier. Slow approvals also cost you money directly. Miss the 10-day window on a 2% early payment discount because your average cycle takes 12 days, and that's roughly £30,000 a year for a company processing £500,000 in monthly invoices. One starting framework for mid-market companies, loosely modelled on the tiered structure in public sector financial delegation policy, looks like this:

Adjust these to your own revenue scale and risk appetite. The person signing off a £200 stationery order shouldn't be the same person approving a £75,000 software contract. If you operate across multiple entities, each entity may need its own thresholds and approvers, especially where local rules or entity-specific budgets apply.

Routing triggers beyond monetary value

Some invoices carry risk that a value-only filter misses. These conditions belong on top of your monetary thresholds:

• First invoice from a new supplier: Route to the procurement process or vendor management regardless of the amount.

• No matching purchase order: Route to the finance controller for an extra validation check.

• Capital expenditure: Require both finance analysis and executive approval.

• Recent change to supplier details (bank account, billing address): Flag for a secondary check. If a supplier's bank details have been fraudulently modified, a verification call to the number on file will reach the fraudster, not the supplier.

An ACCA professional insights report flags a common procurement fraud pattern in which invoices are deliberately priced just under an approval threshold. If senior sign-off kicks in at £5,001, a fraudster submits at £4,999. Review the values sitting just below each of your tier boundaries on a regular basis, so the pattern doesn't hide in plain sight.

You also need to prepare a clear response for when an approver doesn't act.

How to prevent the absent approver problem from stalling a payment run

A well-designed tier matrix only works if someone is always available to approve. In mid-market companies, approval workflows frequently depend on named individuals. Invoices stall when that person is on holiday, travelling, or managing competing priorities.

Document deputies before you need them

For every approval tier, document the primary approver, the deputy, the escalation path if neither is available, and a separate escalation path for suspected fraud. Keep that fraud path deliberately separate. You don't want a suspicious invoice routing through the person being investigated. Get all four in place before someone goes on leave, not after.

Match your escalation timers to invoice value. For routine invoices:

• Tiers 1 to 2 (up to £25,000): Auto-escalate to the deputy after 2 business days.

• Tiers 3 to 4 (£25,001 to £100,000): Auto-escalate to the deputy after 3 business days.

On top of those, add two deadline-driven triggers:

• Approaching payment due date: Alert the finance controller 5 days before the invoice is due to be paid.

• Past payment due date: Escalate to the finance director immediately.

Configure these rules in your AP system and communicate them to every approver before launch. Nobody should be surprised when their overdue approvals start landing on someone else's desk.

Getting budget holders to follow the new workflow

Every approver needs their tier, their deputy, and their SLA before the system starts auto-escalating.

What works is front-loading the communication with a two-week grace period. During that period, the system sends warning notifications but doesn't yet trigger escalation, so approvers can adjust without feeling ambushed. After two weeks, switch to full enforcement. If someone still misses their SLA, the KPI data below will show exactly where, which gives you a specific, numbers-led conversation rather than a general complaint about slow approvals.

Once your tier structure and escalation paths are in place, the remaining bottlenecks tend to be operational.

Automation features that reduce approval cycle time

Manual data entry, PO matching failures, and approvers without system access are the three operational bottlenecks that survive even a well-designed tier structure. If you're evaluating automated invoice processing platforms, these are the capabilities to test against your team's actual stall points.

Intelligent data capture: what to test beyond the demo

OCR accuracy on a clean demo invoice is one thing. OCR accuracy on a scanned PDF with handwritten annotations from a real supplier is another. Manual data entry is where most of your transcription errors start, and where your AP team spends the largest share of its time. How well a platform handles automated capture deserves more weight than most evaluations give it.

When you're evaluating data capture for UK invoices specifically, test against the edge cases your AP team actually hits. Common ones include invoices with multiple VAT rates on the same document, credit notes that need to link to a specific original invoice, self-billing invoices, and supplier templates that change without warning. The real test isn't how well the system handles clean invoices. It's what happens when it can't read one. How quickly does the exception reach a human who can fix it?

Spendesk is an all-in-one spend management platform consolidating company cards, expense management, accounts payable, procurement, and budgeting.

In practice, Spendesk's AP module takes on the capture problems above the moment an invoice arrives. Its AI-powered OCR pulls invoice data automatically, links credit notes to the original invoice they apply to, and flags duplicates before they reach the approval queue. Your AP team only sees genuine exceptions. Clean scans go through untouched.

Automated PO matching and exception handling

When an invoice doesn't match its purchase order (maybe the price is off, or the quantity, or the PO reference is missing), it becomes an exception someone has to resolve manually. These exceptions are where the accounts payable process backs up. Automated two-way and three-way matching, set with sensible tolerance rules, cuts the number of exceptions dramatically. The invoices that genuinely need human attention get it. The rest move through untouched.

The tolerance thresholds you set matter as much as the matching itself. Set them too tight, flagging a £2 rounding difference on a £10,000 invoice, and your exception queue fills with noise. Set them too loose, allowing a 10% variance without review, and you lose the control that matching is supposed to provide.

Most mid-market teams start with a fixed tolerance for small variances (a few pounds) and a percentage tolerance for larger invoices, then adjust after the first month based on exception volume. Can your current system catch a resubmitted invoice where only the date has changed? If it can't, that kind of duplicate or altered resubmission can still slip into the exception queue.

Mobile approvals and multi-channel notifications

Not all your approvers have ERP licences, and hybrid working means they aren't always at their desks. Mobile approvals matter, but two problems show up with multi-channel notifications.

First, fatigue. If your system sends an email, a Slack message, and a push notification for every £50 invoice, approvers will tune all of them out within a week. Match the urgency of the notification to the invoice value and how close the SLA is to breaching.

Second, audit trail gaps. If an approver can action an invoice via email reply or chat message without the action being logged in your AP system, that's a compliance hole. Every approval, whichever channel it comes through, has to write back to the same audit trail.

Without mobile capability, your carefully designed escalation timers will fire more often than they should.

How to know whether your workflow is actually working

Most finance teams don't measure approval workflow performance at all, so there's no baseline and no way to tell whether a redesign is working or where the next bottleneck is forming. Regular, automated spend reporting fixes that.

Track these KPIs by approval tier, by individual approver, and by spend category. That level of detail is what lets you pinpoint whether a bottleneck is a tier-level structural problem or a specific approver's behaviour.

Which of these metrics does your finance team currently report to the CFO?

Establish your baseline before any workflow redesign, then review thresholds after the first 60 days using tier-level exception rate data. If a specific tier is generating disproportionate exceptions, the threshold may need adjustment, or the routing logic may need an additional condition.

Building the workflow your team will actually use

Once you switch on automatic escalation timers and threshold-based routing, every informal workaround your team has been relying on will surface. A department head who routinely rubber-stamps invoices three days late. A finance manager who bypasses the system to avoid a supplier complaint. That friction is worth working through. The alternative is a workflow that depends on everyone staying available and attentive all the time, and that's exactly how approval delays become late payment problems.

A useful invoice approval workflow holds up when your finance director is in a board meeting, a new supplier's first invoice has arrived without a PO, and three department managers haven't actioned their queues since Monday. Start with your current state. Map your invoice management, your approval paths, and every place invoices get stuck. Draft your Delegation of Authority as a governance document. Configure your tiers so the majority of invoices route at the lowest level. Document deputies, set escalation timers, and measure at each level before refining after 60 days.

When it works, your finance team has more control over payments precisely because it isn't involved in every routine approval. The time your team used to spend chasing signatures goes toward analysing spend patterns and negotiating better supplier terms for the CFO.

If you're comparing how different platforms handle tiered approval routing, automated PO matching, and mobile approvals, Spendesk's accounts payable automation shows how it looks in practice. That gives you a concrete benchmark for how much of the manual chasing your team could stop doing.

Frequently asked questions about invoice approval workflows

What happens when an approver consistently misses their SLA?

Start with the data. If your KPIs show one approver averaging five days on a two-day SLA, that's a specific conversation, not a general complaint about slow approvals. Share the numbers, ask whether the threshold or the workload needs adjusting, and agree on a corrective timeline.

If the pattern continues, escalating to the approver's line manager or making the deputy assignment permanent are both reasonable next steps. SLA tracking makes the bottleneck visible so it can be fixed before it becomes a late payment problem.

How often should approval thresholds be reviewed?

Review after the first 60 days of any new workflow, using tier-level exception rate data and individual approver cycle times. After that, a quarterly check is usually enough, unless your company is scaling fast, adding new entities, or changing its supplier base. If a specific tier consistently generates disproportionate exceptions, the threshold or the routing logic likely needs adjustment.

How do you handle approvals when the purchase order and invoice come from different entities?

Multi-entity workflows are where most standard approval logic breaks down. The invoice sits on one entity's books, the PO was raised by another, and the two entities may have different people approving similar amounts. Start by deciding which entity owns the approval for each supplier relationship. That way, the routing logic knows where to send the invoice before it hits a shared queue.

Your AP system should tag every invoice with two entities the moment it arrives: the entity being billed, and the entity that raised the PO. Route the invoice to the approver tier for whichever entity carries the authority. For intercompany transactions (where one entity of your group is billing another), use a separate approval track with finance-team sign-off at both ends. Otherwise an intercompany invoice can move through both approval queues without anyone catching a transfer pricing issue.