The verdict in three sentences
A wholesaler receiving 2,500 supplier invoices a month and spending 1.5 FTE on them can automate capture and three-way matching against purchase orders for anything from 0.25 to 0.85 GBP per invoice on SaaS to 20,000 to 45,000 GBP for a custom build. With AI extraction at around 95% field accuracy and a well-designed approval workflow, the project is delivered in 8 weeks and frees 1 FTE for analysis and supplier dispute work. The UK government has also announced a move toward mandatory B2B e-invoicing later in the decade, so structured invoice handling is worth building now.
Where the 1.5 FTE goes today
At a London building supplies wholesaler, invoices arrive through three channels: PDFs by email, paper with deliveries, and a few large suppliers' portals. Each invoice has to be keyed, matched to the purchase order and goods received note, approved by a buyer when there is a discrepancy, then posted to the ERP.
| Step | Average time per invoice without automation | With AI and automatic matching |
|---|---|---|
| Receipt, sorting and filing | 1.5 min | 0.1 min |
| Keying header and lines | 3.5 min | 0.3 min of review |
| Matching PO and goods received | 2.5 min | Automatic on 75 to 85% of invoices |
| Handling price or quantity differences | 1 min on average | 0.8 min, focused on exceptions |
| Approval and ERP export | 0.5 min | 0.1 min |
| Total | 9 min | about 1.5 min |
On 2,500 invoices, 9 minutes is 375 hours a month, the equivalent of 1.5 FTE after leave and interruptions. At 1.5 minutes it drops to 63 hours, about 0.4 FTE. These are 2026 orders of magnitude seen in wholesale, where invoices often carry 10 to 40 lines.
Accounts payable SaaS or custom build
The UK market offers many accounts payable automation tools, priced per invoice or by bundle. A custom build makes sense when the ERP is specific, line-level matching is complex (different units of sale, footer discounts, pallet deposits) or the business wants to own its matching rules.
| Criterion | Per-invoice SaaS | Custom build |
|---|---|---|
| Cost | 0.25 to 0.85 GBP per invoice, so 7,500 to 25,500 GBP a year at 2,500 invoices a month | 20,000 to 45,000 GBP, then 2,000 to 4,500 GBP a year for hosting and APIs |
| Extraction accuracy | 90 to 97% depending on supplier | About 95%, tuned on your top 50 suppliers |
| Three-way matching | Standard, sometimes header-only | Line by line, wholesale business rules |
| ERP connection | Standard connectors | Dedicated connector to your ERP |
| Lead time | 4 to 8 weeks | About 8 weeks |
| Dependency | Subscription and vendor formats | Code and rules owned by the business |
Both routes can be combined: a SaaS inbox or Peppol access point receives structured invoices, and a custom module performs fine-grained matching and ERP export. See our automation and AI offer.
How three-way matching works
The principle is to compare three documents: the purchase order (agreed prices and quantities), the goods received note (quantities actually received) and the invoice. The AI reads the invoice, including scanned PDFs, and returns extracted fields with a confidence score. The rules engine then compares line by line.
| Situation | Rule applied | Action |
|---|---|---|
| Prices and quantities match | Zero variance | Auto-approval and ERP export |
| Price variance under 1% or 20 GBP | Configured tolerance | Auto-approval with audit trail |
| Price variance above tolerance | Buyer check | Sent to buyer with variance highlighted |
| Invoiced quantity above received quantity | Block | Credit note request to supplier |
| Invoice without PO (fees, services) | Approval workflow | Sent to budget owner |
| Low extraction confidence | Human check | Only doubtful fields reviewed |
The approval workflow is the key success factor: if buyers take 10 days to clear exceptions, automation shortens nothing. A dashboard of pending invoices by approver with automatic 48-hour reminders solves this.
Mini case study
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Sarah, finance manager of a building supplies wholesaler in London, processes 2,500 invoices a month with 1.5 FTE costing 38,000 GBP fully loaded per FTE per year.
- Current cost: 1.5 × 38,000 GBP = 57,000 GBP a year.
- Custom option chosen: 32,000 GBP of development, plus 3,500 GBP a year for hosting and AI API calls. After the project, 0.5 FTE remains on review, so 19,000 GBP a year.
- Yearly saving: 57,000 GBP minus 19,000 GBP minus 3,500 GBP, so 34,500 GBP a year. The build pays back in about 11 months.
- Secondary gain: invoices are posted in 3 days instead of 12, which lets the firm take early payment discounts offered by some suppliers, typically 0.5 to 2%.
The freed FTE moves to supplier dispute follow-up and margin analysis, two tasks the team kept postponing.
FAQ
Is AI reliable on poor-quality scanned invoices?
On legible scans, accuracy is around 95% of fields. On crumpled or handwritten documents it falls toward 80%, but the system flags doubtful fields and never auto-approves an invoice with a low confidence score.
What does UK e-invoicing policy change?
The government has announced plans for mandatory B2B e-invoicing later in the decade, built on structured formats such as Peppol. Structured invoices greatly reduce extraction work, but matching against purchase orders is still needed.
How long does it take to configure the top 50 suppliers?
About 2 weeks within the 8-week project. These 50 suppliers often represent 70 to 80% of a wholesaler's invoice volume.
Does our accounting data go to an AI provider?
Calls can go through APIs hosted in the UK or EU, with no reuse of data for model training. Check the data processing agreement and retention period under UK GDPR before launch.
Do we need to change ERP?
No. The connector exports approved entries into your existing ERP, by file or API. Only an ERP with no import capability at all requires extra development, priced in the quote.
Let's scope your project. Send us a sample of 50 anonymised invoices and the name of your ERP, and we will estimate the achievable automation rate and an 8-week plan. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
