The verdict in three sentences
For a Dublin firm with 600 small business clients, a custom client portal budgets at 28,000 to 45,000 EUR excluding VAT, delivered in 12 weeks. The line that moves the invoice is not the interface but the connector to the practice management software (syncing clients, deadlines and documents). The return comes mostly from chasing: about 2 full-time equivalents freed from hunting for receipts and statements.
What an accounting firm client portal contains
The typical need of a 15 to 25 person firm fits into four modules. Small business clients upload invoices and bank statements from their phone, e-sign their engagement letter, see their upcoming deadlines (VAT returns, preliminary tax, payroll filings, annual accounts) and message their accountant without endless email threads. On the firm side, a dashboard shows who is late and triggers automated reminders.
| Module | Scope | Estimated 2026 budget (EUR excl. VAT) | Share of project |
|---|---|---|---|
| Document upload | Mobile upload, basic OCR, filing by financial year | 6,000 to 9,000 | 20 % |
| Engagement letter | Templates, eIDAS e-signature, archiving | 3,500 to 6,000 | 12 % |
| Tax calendar | Per-client calendar, email and SMS alerts | 4,000 to 7,000 | 15 % |
| Messaging and reminders | Thread per client file, scheduled reminders | 3,500 to 6,000 | 13 % |
| Practice software connector | API or scheduled import, client mapping | 7,000 to 11,000 | 25 % |
| Security, GDPR, testing | Two-factor auth, access log, QA | 4,000 to 6,000 | 15 % |
| Total | 12 weeks | 28,000 to 45,000 | 100 % |
No health-data certification is needed for an accounting firm, but hosting inside the European Union is required in practice: tax data, bank details and payslips fall under GDPR and professional confidentiality rules. Budget 150 to 400 EUR per month with an EU cloud provider.
Custom build or the portal bundled with your practice software
Most practice software vendors offer a client portal add-on. It is often enough for a 200-client firm, much less so for 600 clients with their own chasing process.
| Criterion | Bundled vendor portal | SaaS document collection tool | Custom portal |
|---|---|---|---|
| Entry cost | 0 to 3,000 EUR | 1,500 to 4,000 EUR setup | 28,000 to 45,000 EUR |
| Annual cost (600 clients) | 4,000 to 9,000 EUR | 6,000 to 12,000 EUR | 3,500 to 7,000 EUR (hosting, maintenance) |
| Reminder customization | Low | Medium | Full |
| Firm branding | Logo only | Logo and colors | Full experience under the firm's name |
| Vendor lock-in | High | Medium | Low, code owned by the firm |
| Time to go live | 2 to 4 weeks | 4 to 6 weeks | 12 weeks |
| 5-year cumulative cost (estimate) | 20,000 to 48,000 EUR | 31,500 to 64,000 EUR | 45,500 to 80,000 EUR |
Custom is not the cheapest over 5 years. It pays off when the firm wants to industrialize its chasing, sell extra services (management dashboards, advisory) or prepare acquisitions by onboarding other practices onto the same tool.
Typical 12-week plan
| Weeks | Deliverable | Firm involvement |
|---|---|---|
| 1 to 2 | Workshops, client journey, connector specs | 2 half-days with a partner and a manager |
| 3 to 6 | Document upload, calendar, back office | 45-minute weekly review |
| 7 to 9 | Practice software connector, e-signature | API access or exports provided by the vendor |
| 10 | Internal testing with 5 staff | 1 day of testing |
| 11 | Pilot with 40 volunteer clients | Feedback gathered by the firm |
| 12 | Rollout to 600 clients, training | Email campaign and video tutorial |
The main risk is access to practice software data: some vendors charge for their API (often 1,000 to 3,000 EUR per year) or only expose scheduled exports. Check this before signing the quote.
Mini case study
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Aoife, partner in a 20-person firm in Dublin, serves 600 small businesses. Her team spends on average 6 hours per month per person chasing missing documents, so 120 hours a month across 20 people, or about 0.9 FTE. Add the rekeying of documents received by email (an estimated 1.1 FTE) and you reach 2 FTE. At a loaded cost of 52,000 EUR per FTE, the stake is 104,000 EUR per year. If the portal recovers 60 % of that time, the gain is 62,400 EUR a year. For a 38,000 EUR project plus 5,000 EUR of annual running costs, payback comes in 8 to 9 months, and the freed time goes to billable advisory work.
FAQ
How much does a client portal for an accounting firm cost in 2026?
Budget 28,000 to 45,000 EUR excluding VAT for a custom portal covering document upload, engagement letters, a tax calendar and a connector. A minimal version without the connector starts around 18,000 EUR.
Do we need specialist certified hosting?
No, health-data certifications do not apply. EU hosting with encryption and an access log is strongly recommended, at 150 to 400 EUR per month.
Is an e-signed engagement letter valid?
Yes, a simple or advanced electronic signature compliant with eIDAS is enough for an engagement letter. A signature provider costs around 1 to 3 EUR per envelope or an annual plan.
How many clients actually use the portal?
With a small business base, expect 55 to 70 % adoption after 6 months if the firm stops accepting documents by email. Without that rule, adoption often stays below 35 %.
Who owns the code?
With a custom build, the firm should secure an assignment of rights in the contract. Ongoing maintenance is then typically negotiated at 3 to 6 days per quarter.
Let's scope your project. We scope your client portal (modules, connector to your practice software, a 28,000 to 45,000 EUR budget, delivery in 12 weeks) from your current processes. 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.
