The verdict in three sentences
For an accountancy practice with 350 clients, AI classification and pre-coding of source documents removes 50 to 70% of manual entry, provided a team member reviews the low-confidence items. Off-the-shelf tools like Dext and AutoEntry cover most needs from about GBP 30 to 60 per client per month at scale, while a custom layer runs GBP 35,000 to 80,000 in London in 2026. Custom only makes sense when your workflow, client mix or data residency rules do not fit the standard tools.
The problem: 350 clients, documents arriving in a mess
A London practice with 3 partners and 14 staff receives about 9,000 documents a month: phone photos of receipts, emailed PDFs, bank statements, scanned till slips. Around VAT quarter-ends and Self Assessment season, the team is swamped and files fall behind.
| Document type | Monthly volume | Current pain | Target automation rate |
|---|---|---|---|
| Supplier invoices (PDF) | 3,200 | Supplier, VAT, nominal code | 75 to 85% |
| Invoice photos (phone) | 2,100 | Variable quality, cropping | 55 to 70% |
| Bank statements | 900 | Line-by-line reconciliation | 80 to 90% |
| Sales invoices | 1,800 | Numbering, output VAT | 70 to 80% |
| Receipts, expenses | 700 | Legibility | 40 to 55% |
| Contracts, letters | 300 | Filing only | 90% filing, no coding |
The target flow: central intake (dedicated email, mobile upload, portal), OCR, classification by client and type, pre-coding against each client's chart of accounts, then a human review queue for items below a confidence threshold, often 90%.
Off-the-shelf vs custom: 2026 costs
| Option | Upfront | Recurring | Fit |
|---|---|---|---|
| Dext Prepare (practice plan) | Low, onboarding time | Roughly GBP 30 to 60 per client per month at practice scale | Strong for Xero/QuickBooks/Sage clients |
| AutoEntry | Low | Credit-based, roughly GBP 10 to 60 per client per month by volume | Good for variable volumes |
| Native Xero / QuickBooks capture | None | Included in some plans | Basic, limited rules |
| Custom AI layer (London market) | GBP 35,000 to 80,000 | Hosting plus GBP 0.03 to 0.15 per document | Specific workflows, data residency, own portal |
| Hybrid: Dext + custom review dashboard | GBP 10,000 to 25,000 | Dext fees plus hosting | Practice-wide KPIs on top of a standard tool |
At Kolonell, a full custom layer is a complex custom application, 7,000,000 to 15,000,000+ FCFA (10,670 to 22,870+ EUR) on our grid, or medium complexity at 4,000,000 to 7,000,000 FCFA (6,100 to 10,670 EUR) if limited to PDF invoices and bank statements.
What you must lock down
Human review. The AI suggests, a bookkeeper approves. The practice keeps professional responsibility under ICAEW or ACCA rules; nothing posts without approval below the confidence threshold.
UK GDPR. Client documents contain personal data. You need a lawful basis, a data processing agreement with every provider, UK or EU hosting (or adequate transfer safeguards) and a documented retention period, typically 6 years for HMRC records.
Learning per client. The same supplier may go to different nominal codes for different clients. The model must remember choices per client.
Export and MTD. Check that coded entries flow into Xero, QuickBooks or Sage cleanly so Making Tax Digital VAT returns stay intact.
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Priya, managing partner of a London practice, estimates 2.5 minutes of entry per document. On 9,000 documents: 9,000 × 2.5 = 22,500 minutes, or 375 hours a month, more than 2 full-time bookkeepers.
With 60% of entry removed and 0.5 minute of review on automated items: (3,600 × 2.5) + (5,400 × 0.5) = 9,000 + 2,700 = 11,700 minutes, or 195 hours. Saving: 180 hours a month. At a loaded GBP 32 an hour, that is GBP 5,760 a month, or GBP 69,120 a year.
With Dext at an average GBP 40 per client for 350 clients, the subscription is GBP 14,000 a month, though most practices only enrol the clients with document volume, say 150 clients at GBP 6,000 a month. A GBP 60,000 custom build plus GBP 900 a month of variable cost pays back in about 12 months against the time saved, and beats the subscription after roughly a year. The trade-off is ownership of maintenance.
FAQ
How accurate is OCR on phone photos?
2026 engines read clean printed invoices at 95%+ field accuracy. Crumpled receipts and handwriting stay harder and mostly land in the review queue.
Do we need to change accounting software?
No, coded entries are exported to Xero, QuickBooks or Sage through their APIs. That covers over 90% of UK small business clients.
How long until suggestions are reliable?
Allow 4 to 8 weeks of live use. Correct pre-coding usually rises from 60% to over 80% on recurring clients.
Will clients have to change habits?
Barely: they keep sending photos and PDFs, just to one address or upload link. A simple portal raises the share of usable documents by around 15%.
Where are documents stored?
In the UK or EU, encrypted, with named access and retention aligned with HMRC's 6-year requirement.
Let's scope your project. Send us an anonymised sample of 200 documents and your accounting software, and we will measure the achievable automation rate and scope an 8 to 12 week rollout. 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.
