The verdict in three sentences
For a 25-person practice with 600 clients, an off-the-shelf client portal billed at 3 to 8 GBP per client per month costs 21,600 to 57,600 GBP a year, so over three years more than a custom-built portal at 30,000 to 80,000 GBP. A custom build makes sense once your engagement letters, chasers and review workflow go beyond the standard, or once the practice passes 400 active clients. With 4 to 6 hours saved per client per year on document collection, the investment usually pays back within one financial year.
Off-the-shelf portal or custom build: the 2026 numbers
Market portals (client spaces bundled with practice software, document collection platforms) are quick to switch on, but their cost scales with your client count. A custom build is expensive in year one, then costs little beyond maintenance. Here are 2026 estimates for a London practice with 600 clients.
| Criterion | Off-the-shelf portal | Custom portal |
|---|---|---|
| Upfront cost | 0 to 2,500 GBP of setup | 30,000 to 80,000 GBP |
| Recurring cost | 3 to 8 GBP per client per month, i.e. 21,600 to 57,600 GBP a year | Maintenance at 10 to 15 % a year, i.e. 3,000 to 12,000 GBP |
| Time to go live | 2 to 6 weeks | 10 to 16 weeks |
| Integration with your ledger | Standard connectors, sometimes paid | Dedicated Xero API integration, plus your practice software |
| Practice-specific workflow | Limited to vendor options | Checklists per engagement, chasers, internal sign-off |
| Ownership of code and data | Licence, vendor lock-in | Code and data owned by the practice |
| 3-year total cost | 64,800 to 172,800 GBP | 39,000 to 116,000 GBP |
The tipping point sits around 300 to 400 clients: below that, a well-chosen SaaS remains cheaper. Above it, or if you want a branded experience with steps tailored to payroll, VAT, Making Tax Digital and year-end engagements, the custom build wins.
The features that save 4 to 6 hours per client
The gain does not come from the portal itself but from the end of email chasers, missing documents discovered at review stage and re-keying. Here are the building blocks that matter and their indicative development cost.
| Feature | Time saved per client per year | Indicative development cost |
|---|---|---|
| Document collection with checklist per engagement type | 1.5 to 2 h | 6,000 to 12,000 GBP |
| Automatic email and SMS chasers until receipt | 1 to 1.5 h | 2,500 to 6,000 GBP |
| E-signature of engagement letters and AML onboarding | 0.5 h | 3,000 to 6,000 GBP |
| Two-way Xero sync (contacts, bank feeds, documents) | 1 to 1.5 h | 8,000 to 20,000 GBP |
| Secure messaging attached to each client file | 0.5 to 1 h | 3,500 to 8,000 GBP |
| Deadline calendar for VAT, payroll and self-assessment | 0.5 h | 4,000 to 10,000 GBP |
Add 15 to 20 % for design, project management and testing. On compliance, the portal must encrypt documents, enforce two-factor authentication, log access and keep data in the UK or EU, in line with UK GDPR and ICO guidance.
At Kolonell, a client portal of this scope falls into the medium application band: 4,000,000 to 7,000,000 FCFA (6,100 to 10,670 EUR), with maintenance at 35,000, 75,000 or 120,000 FCFA a month depending on the service level. The GBP figures above are London market estimates.
How to scope the project without drift
A successful portal starts small. Scoping (2 weeks) lists your engagement types, the documents expected for each and the must-have integrations. The first release (8 to 10 weeks) delivers collection, chasers and messaging. A one-month pilot with 50 volunteer clients lets you fix usability before the full rollout. Deeper Xero sync and the deadline calendar come in a second release, once adoption is measured. Aim for 70 % of clients active on the portal after six months: that is the threshold at which manual chasing truly disappears.
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Illustrative example: Sarah, managing partner of a 25-person accounting practice in London, looks after 600 clients. Her team spends on average 4 hours per client per year chasing and sorting documents, i.e. 2,400 hours. At a loaded cost of 38 GBP an hour, that is 91,200 GBP a year. A custom portal at 50,000 GBP, plus 7,000 GBP of yearly maintenance, pays back in 50,000 / 91,200 x 12, i.e. about 6.6 months. By comparison, a SaaS at 5 GBP per client would cost 36,000 GBP every year, indefinitely.
FAQ
How much does a client portal for an accounting firm cost in 2026?
Expect 3 to 8 GBP per client per month for a SaaS, and 30,000 to 80,000 GBP for a custom portal in London. At Kolonell, a medium application of this type costs 4,000,000 to 7,000,000 FCFA (6,100 to 10,670 EUR).
How long until the portal is live?
A first usable release takes 10 to 12 weeks, scoping included. Then plan a one-month pilot with around fifty clients before the full rollout.
Can the portal connect to Xero?
Yes. Xero exposes a well-documented API covering contacts, invoices, bank transactions and files. The connector costs 8,000 to 20,000 GBP depending on the depth of synchronisation.
How do we get clients to actually use it?
By making upload easier than email: phone photo upload, a clear checklist, automatic chasers. Practices that support the launch reach 60 to 75 % adoption within six months.
Who owns the data and the code?
With a custom build, the practice owns both the code and the data, hosted in the UK or EU. You can switch maintenance provider without any migration.
Let's scope your project. Send us your client count, engagement types and ledger software: we price the client portal in releases, with an indicative budget and a 10 to 16 week timeline. 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.
