The verdict in three sentences
A retail group in London receiving 3,500 supplier invoices a month typically ties up three to four full-time accounts payable staff on data entry, chasing and answering the phone. A supplier portal with invoice upload, status tracking and ERP matching cuts supplier calls by about 60 % and halves processing time. London agencies quote this kind of project at 60,000 to 140,000 GBP; the Kolonell grid places it at high complexity, 7,000,000 to 15,000,000 FCFA (10,670 to 22,870 EUR excl. VAT), with a 14-week timeline.
The hidden cost of manual invoice processing
The CFO sees the invoice, not the workflow. Every paper invoice or emailed PDF follows the same route: receipt, entry, finding the purchase order, approval, payment run. Then the supplier calls to ask where the payment is.
| Indicator (3,500 invoices a month, London) | Manual workflow | With supplier portal |
|---|---|---|
| Entry time per invoice | 6 to 8 min | 1 min (check only) |
| Supplier calls and emails per month | 1,200 | 480 |
| Average approval time | 18 days | 7 days |
| Duplicate or miscoded invoices | 2 to 3 % | under 0.5 % |
| AP FTEs involved | 3.5 | 1.5 |
| Estimated annual processing cost (loaded salary 3,800 GBP per month) | 159,600 GBP | 68,400 GBP |
These figures are a 2026 order of magnitude. The main gain comes from the end of chasing: suppliers check their invoice status themselves, as they would track a parcel.
The approval steps to model
A useful portal mirrors your approval workflow exactly, otherwise teams bypass it. Here is the typical workflow of a retail group with central purchasing and stores.
| Step | Actor | Automatic check | Indicative build cost |
|---|---|---|---|
| PDF or e-invoice upload | Supplier | Format, duplicate, VAT number | Included in core |
| OCR reading of amounts | System | Net, VAT 20 %, gross extraction | 12,000 to 24,000 GBP (market estimate) |
| PO and goods receipt matching | System and buyer | Price or quantity variance above 2 % | 16,000 to 32,000 GBP (market estimate) |
| Budget approval | Management accountant | Threshold per cost centre | 6,000 to 10,000 GBP |
| Approval to pay | CFO above 50,000 GBP | Dual approval | Included |
| Export to ERP and payment run | Treasury | Journal entry generated | 12,000 to 28,000 GBP depending on ERP |
| Status notification | Supplier | Email and dashboard | Included |
The ERP connector weighs heavily in the budget: a modern API (Sage, NetSuite, Business Central) plugs in within weeks, an older ERP without an API forces more fragile file exchanges.
Overall budget: local agency or Kolonell grid
| Item | London agency (market estimate) | Kolonell |
|---|---|---|
| Full portal with ERP matching | 60,000 to 140,000 GBP | 7,000,000 to 15,000,000 FCFA (10,670 to 22,870 EUR excl. VAT) |
| Timeline | 16 to 24 weeks | 14 weeks |
| Hosting | 300 to 800 GBP per month | Included in maintenance |
| Maintenance | 1,000 to 2,500 GBP per month | 120,000 FCFA per month (180 EUR) at Premium level |
| Equivalent SaaS licence (market estimate) | 0.50 to 1.20 GBP per invoice, i.e. 21,000 to 50,000 GBP a year | No per-invoice licence |
At 3,500 invoices a month, a SaaS billed per document soon costs more than a custom portal from year two. Custom also makes sense for compliance: VAT records under Making Tax Digital and readiness for UK e-invoicing.
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Illustrative example: James, CFO of a 22-store retail group in London, processes 3,500 invoices a month with 3.5 AP staff. He estimates the annual workflow cost at 159,600 GBP. With the portal, he moves two staff to management control, i.e. 91,200 GBP of time recovered per year. He adds a 1 % early-payment discount on 15 % of invoices, about 24,000 GBP. For a project at 11,000,000 FCFA (about 16,770 EUR), payback is around two months.
FAQ
How much does a supplier portal cost in London in 2026?
Local agencies quote 60,000 to 140,000 GBP according to our market estimates. The Kolonell grid places a portal with ERP matching at high complexity, 7,000,000 to 15,000,000 FCFA, i.e. 10,670 to 22,870 EUR excl. VAT.
Will suppliers actually use the portal?
Yes if uploading takes under two minutes and payment status is visible. Groups that make the portal mandatory within 90 days usually reach 80 % adoption.
Is the portal ready for e-invoicing?
It can be if it is built around a structured format from day one. Planning for it adds about 10 % to the initial budget and avoids a rebuild.
What timeline for a group with 3,500 invoices a month?
Allow 14 weeks: 3 for scoping, 8 for development and 3 for acceptance testing with a panel of 20 pilot suppliers.
Can we start without automatic matching?
Yes, a first version with upload and status tracking falls under medium complexity, 4,000,000 to 7,000,000 FCFA. ERP matching is added in phase two.
Let's scope your project. Share your invoice volume, ERP and approval workflow: we define the scope, an indicative budget between 7,000,000 and 15,000,000 FCFA and a 14-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.
