The verdict in three sentences
For a London practice with 900 clients, an off-the-shelf client portal costs about GBP 4,500 to 16,200 a year (GBP 5 to 18 per client, 2026 market ballpark) and is the right first step for most firms. A custom portal at GBP 20,000 to 45,000 pays off when you run quarterly Making Tax Digital workflows at scale, want deep Xero automation and need AML onboarding built in. Whichever you choose, measure it on one number: hours saved chasing records per client per year.
What chasing actually costs a 15-person practice
| Metric | Value | Basis |
|---|---|---|
| Clients | 900 | Mix of limited companies, sole traders, landlords |
| Chasing time per client per year | 2.5 h | Emails, calls, reminders, reconciling gaps |
| Total chasing hours | 2,250 h | 900 × 2.5 |
| Loaded staff cost | GBP 38/h | 2026 estimate, London |
| Annual cost of chasing | about GBP 85,500 | 2,250 × 38 |
| Target reduction | 40% | Automated requests, reminders, upload links |
| Hours released | 900 h | Roughly half a full-time employee |
The pressure is rising: Making Tax Digital for Income Tax is being phased in for sole traders and landlords above an income threshold starting April 2026, which turns annual paperwork into quarterly updates. Check current thresholds and dates on GOV.UK rather than relying on any summary, including this one.
Custom vs SaaS for a UK practice
| Criterion | SaaS portal | Custom portal |
|---|---|---|
| Upfront cost | Setup, often low | GBP 20,000 to 45,000 |
| Annual cost | GBP 4,500 to 16,200 | Support GBP 5,000 to 10,000 |
| Go-live | 2 to 6 weeks | 3 to 5 months |
| Xero integration | Standard sync if offered | Custom rules per client type |
| MTD quarterly workflows | Generic reminders | Per-client calendar, bridging data checks |
| AML onboarding (ID, risk assessment) | Often a separate tool | Built into the client journey |
| Data ownership and exit | Vendor export | Code and data are yours |
Over five years, SaaS costs GBP 22,500 to 81,000 and custom GBP 45,000 to 95,000 including support. The custom route only wins if your workflows are genuinely non-standard, for example a heavy landlord book under MTD or a monthly management accounts service.
Data sits under UK GDPR: host in the UK or a jurisdiction with UK adequacy, encrypt documents, and sign a processing agreement with your developer and host. As a nearshore option, Kolonell's prices for a medium-complexity custom application run from EUR 6,100 to 10,670 (4,000,000 to 7,000,000 FCFA), with Standard maintenance at EUR 114 per month (75,000 FCFA).
Mini case study
Illustrative example: Daniel, managing partner of a 15-person practice in Islington, 900 clients including 260 landlords about to enter quarterly MTD. A SaaS portal at GBP 12 per client costs GBP 10,800 a year, GBP 54,000 over five years. A custom portal costs GBP 34,000 plus GBP 7,000 a year, GBP 69,000 over five years.
The GBP 15,000 gap is covered if custom saves about 395 more hours than SaaS over five years (15,000 / 38), roughly 80 hours a year, or 18 minutes per landlord client per year. Daniel pilots the SaaS on 150 clients for one quarter; if MTD reminders still need manual tracking, he moves to custom with a specification shaped by the pilot.
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
FAQ
How much does a client portal cost for 900 clients?
As a 2026 market ballpark, GBP 4,500 to 16,200 a year for SaaS. A custom build needs GBP 20,000 to 45,000 upfront plus GBP 5,000 to 10,000 a year in support.
Can a custom portal integrate with Xero?
Yes, through Xero's public API, subject to its developer terms. Budget 10% to 20% of the project for integration and test on 20 real clients.
Does Making Tax Digital make a portal essential?
Quarterly updates multiply the number of collection cycles by four for affected clients. Without automation, chasing time rises sharply, which is why many practices act in 2026.
Can AML checks be part of the portal?
Yes: ID upload, risk questionnaire and annual review reminders can sit in the onboarding flow. Many practices save 30 to 45 minutes per new client this way.
How long does a custom build take?
Plan 3 to 5 months including a pilot on 50 to 100 clients. Avoid launching in January, the self-assessment peak.
Let's scope your project. Tell us your client count, practice software and MTD exposure, and we will price the portal, Xero integration and pilot plan. 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.
