The verdict in three sentences
An AI document-processing solution (OCR + LLM) for a professional firm in London costs between GBP 9,000 and GBP 24,000 in 2026, depending on document types and integration with your accounting software. It automates 70 to 90% of invoice, statement and expense data entry, at a marginal cost of a few pence per document. Payback lands in 4 to 7 months thanks to the entry hours saved during closing periods.
What the solution actually does
The OCR + LLM combo does more than "scan": it reads a supplier invoice, extracts the vendor, date, net, VAT and gross, suggests an account code and a cost centre, then pushes a pre-filled entry into your tool. The accountant validates instead of typing. It is the shift from a data-entry job to a control job.
| Function | Without AI | With AI | Gain |
|---|---|---|---|
| Supplier invoice entry | 2-4 min | 15-30 s | ~85% |
| Accounting categorization | Manual | Suggested | ~80% |
| Bank statement reconciliation | 1-2 h/month/client | 10-20 min | ~80% |
| Expense claims | 3-5 min/item | 20 s | ~90% |
| Entry error rate | 3-5% | < 1% | -70% |
The real automation rate depends on the quality and variety of your documents. A stream of recurring invoices from usual suppliers quickly reaches 90%; handwritten or exotic items stay in human validation.
Cost, and the per-document price
The project budget splits between setup and usage cost. Here are 2026 orders of magnitude.
| Item | 2026 range (GBP) | Detail |
|---|---|---|
| Scoping & document sampling | 1,300 - 2,600 | Flow analysis, chart of accounts |
| OCR + LLM engine & prompts | 3,000 - 8,600 | Extraction, categorization rules |
| Accounting software integration | 2,600 - 7,700 | Connector, import format, checks |
| Validation interface | 1,300 - 3,400 | Queue, corrections, learning |
| Acceptance & training | 400 - 1,700 | Tests on your real files |
| Cost per processed document | GBP 0.02 - 0.13 | LLM tokens + OCR, pay per use |
| Monthly subscription | 170 - 500 | Hosting, monitoring, support |
At GBP 0.07 per document and 8,000 documents/month, usage cost is around GBP 560/month, far below the cost of the entry hours replaced.
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Mini case study
Ms Ferreira, partner at an accounting firm in London (14 staff, 320 clients), processes about 9,000 invoices a month. Data entry ties up 2.5 FTEs during closing, i.e. ~GBP 10,000/month in cost. She invests GBP 16,000 in an AI extraction engine integrated with her software, plus GBP 480/month of usage. At 82% automation, she frees roughly 1.8 FTE, redeployed to billable advisory work of higher value. Estimated net saving: ~GBP 7,000/month. The upfront investment is recovered in about 4 months, after which the gain becomes recurring and the firm scales capacity without hiring.
FAQ
What automation rate can I realistically expect? Between 70 and 90% depending on how standardized your documents are. Recurring supplier invoices reach 90%; atypical items stay in human validation, which is normal and intended.
How much does processing one document cost? In 2026, expect GBP 0.02 to 0.13 per document in token and OCR cost. At accounting volumes, that is negligible against the entry time saved.
Is my client data protected? Yes. We favour UK/EU hosting and, if needed, no-retention LLM models. Access is partitioned per client file and logged for compliance.
Is it compatible with my accounting software? In most cases yes, via file import or API. The connector represents GBP 2,600 to 7,700 depending on how open your tool is.
How long until it is live? Plan for 5 to 8 weeks from scoping to production on your real files, including learning on your documents.
Let's scope your project. Tell us your monthly document volume, your accounting software and your document types, and we'll price the automation and its ROI. 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.
