Client Portal for an Accounting Firm in London: Document Exchange, e-Sign and Cost (2026)

The verdict in three sentences

Exchanging accounting documents by email costs you more than a secure extranet: between chasing, lost files and GDPR risk, each staff member loses around 6 hours a week. A custom portal connected to your production tool (Cegid, IRIS, CCH) is priced in 2026 at roughly 18,000 to 40,000 EUR for delivery in 10 to 16 weeks. If you handle more than 150 client files, the investment pays back in under two years through recovered admin time.

Three ways to digitise document exchange

The first instinct is to switch on your accounting software's built-in portal. It is fast, but the client experience stays rigid and your firm's brand disappears behind the vendor's. At the other end, a generic file-sharing SaaS is cheap but does not connect to your production: you re-key everything. A custom extranet costs more upfront but aligns with your processes (document management, approval workflow, e-signature).

E-signature is billed separately: budget 0.50 to 2 EUR per document depending on the provider (simple or advanced eIDAS level) and your negotiated annual volume.

What a production-system connection changes

The real gain is not file upload, it is the removal of double data entry. When a client uploads an invoice, the extranet files it in the right folder, notifies the accountant and pre-fills the metadata. An API connection to your production tool avoids manually re-importing each document.

Hosting should stay within the EU to respect GDPR and professional confidentiality: budget 100 to 250 EUR per month for certified infrastructure with encrypted backups.

Mini case study

Mark, partner at a 14-person firm in London, handles 320 files. Each staff member loses 6 h/week chasing documents, an all-in cost of roughly 28 EUR/h x 6 x 14 = 2,352 EUR per week, over 100,000 EUR a year of unproductive time. He invests 32,000 EUR in an extranet connected to his production tool, plus 200 EUR/month hosting and 900 EUR/year for signatures. By cutting chasing to 1 h/week, he recovers the equivalent of over 80,000 EUR a year of time. Payback in about 5 months, on top of a premium image with clients.

FAQ

How much does a client extranet for an accounting firm cost in 2026?

Expect a ballpark of 18,000 to 40,000 EUR for a custom portal connected to your production tool, and up to 55,000 EUR with advanced DMS and OCR. A vendor module stays under 2,000 EUR/year but without customisation.

How long does it take to set up?

Between 10 and 16 weeks for a connected version: 3-4 weeks of scoping and design, 6-10 weeks of development, 2-3 weeks of testing and migrating existing files.

Is it GDPR and confidentiality compliant?

Yes, provided you host in the EU with encryption at rest and in transit, access logs and a data processing agreement (DPA). This foundation represents 100 to 250 EUR/month of certified hosting.

Can e-signature be integrated?

Yes, via an eIDAS provider. The cost is 0.50 to 2 EUR per document, negotiable by volume. A tax return signed online drops from 5 days by post to 10 minutes.

Isn't a generic SaaS at 150 EUR/month better?

For a very small firm, yes, but it does not connect to your production tool: you re-key every document. Beyond 150 files, the wasted time quickly exceeds the cost of a custom extranet.

Let's scope your project. Tell us your file volume, production tool and signature needs: we will frame a scope between 18,000 and 40,000 EUR. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.