Client portal for an accounting firm in London: 2026 cost

The verdict in three sentences

For a London accounting firm with 900 clients, a custom client portal costs between 6,100 and 10,670 EUR excl. VAT with Kolonell (one connector included at medium complexity), versus 3 to 8 EUR per client per month for an off-the-shelf solution, which means 97,000 to 259,000 EUR over 3 years at that volume. Custom build becomes the better deal once the portfolio exceeds roughly 250 active clients and the firm wants a workflow that matches its own production method. Below that, or if nobody internal can own the project, a licence remains the sensible choice.

What the portal must do, module by module

A useful portal replaces three flows that currently swamp staff inboxes: collecting supporting documents, signing accounts and engagement letters, and recurring client questions. Everything else is secondary at launch. Here are the modules, their share of the budget and what they require technically (2026 order of magnitude, 10 to 14 week project).

Two items derail budgets. The first is the connector: depending on the practice software, it ranges from a scheduled CSV export to a real API. On the market, agencies often bill it separately, between 2,000 and 5,000 EUR excl. VAT (market estimate); in the Kolonell grid it stays within the medium complexity range as long as only one software is involved. The second is client migration: importing 900 records with contacts, mandates and year ends takes one day of data cleaning on the firm's side.

Licence or custom build: the 3-year calculation

Off-the-shelf solutions charge per active client. At 900 clients the gap widens quickly. Assumptions: licence at 4 EUR per client per month (mid range), Kolonell custom build at 9,800 EUR excl. VAT connector included, Kolonell Standard maintenance at 110 EUR per month (75,000 FCFA).

The honest reading of this table: a licence funds a product team that keeps improving the tool, which a custom build does not do without an evolution budget. But at this volume the firm can set aside 5,000 EUR a year for improvements and still be three times cheaper. The break-even point sits around 200 to 250 active clients: below that, the licence wins.

Security and compliance, the DPO's questions

An accounting portal handles payslips, bank statements and tax computations. Minimum 2026 requirements: hosting in the UK or EU, encryption at rest and in transit, two-factor authentication for staff, access logs kept for 12 months, and configurable deletion of documents after the legal retention period. The firm's UK GDPR record of processing must list the portal, with the hosting provider as processor.

Mini case study

Illustrative example: Helen, partner at an accounting firm in London (14 staff, 900 small business clients). Her managers spend on average 6 minutes per client per month chasing, sorting and renaming documents received by email, which adds up to 90 hours a month. The portal removes about 60 % of that, or 54 hours.

At a loaded hourly cost of 45 EUR, the saving reaches 2,430 EUR a month, or 29,160 EUR a year. First-year investment (9,800 + 1,800 + 1,320) comes to 12,920 EUR excl. VAT. Payback arrives after 5 to 6 months, before even counting accounts signed earlier during the filing season.

FAQ

How long does it take to deliver a client portal for an accounting firm?

Plan for 10 to 14 weeks: 2 weeks of scoping, 7 to 9 weeks of development and 2 weeks of acceptance testing with 20 to 30 pilot clients. Launching outside the January self assessment peak avoids training clients at the worst moment.

Can the portal connect to IRIS, CCH or Xero Practice Manager?

Yes, depending on each vendor's options: documented API, partner connector or scheduled export. The connector represents about 20 % of the budget and must be validated technically in the first week of scoping.

Does the firm own the code?

Yes, the code and data belong to the firm, which avoids vendor lock-in. Kolonell maintenance (35,000, 75,000 or 120,000 FCFA a month, i.e. 50, 110 or 180 EUR) covers security updates and bug fixes.

Will older or less tech-savvy clients use it?

Uploading a photo from a phone, with no app to install, is usually enough to bring 70 to 80 % of clients on board within 6 months (order of magnitude seen on this type of tool). Email stays open for the rest during the transition.

What does e-signature cost?

On the market, a simple signature costs 1 to 2 EUR each, an advanced one slightly more. For 900 accounts and engagement letters a year, budget 900 to 1,800 EUR annually, included here in the hosting line.

Let's scope your project. Client portal with document upload, e-signature and a connector to your practice software: indicative budget 6,100 to 10,670 EUR excl. VAT (4,000,000 to 7,000,000 FCFA), delivered in 10 to 14 weeks. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.