How Much Does a Custom Web App, Portal or Booking System Cost?

The honest answer

A custom web app, portal or booking system typically costs anywhere from around £10,000 to well over £50,000 to build — and, like a bespoke website, the range isn't about some studios overcharging. It's because "a web app" covers everything from a single-purpose tool that does one job to a full platform running a chunk of the business.

The reason it costs more than a standard website is simple: a brochure site mostly shows information; an app does things. It handles logins, stores and moves data, enforces rules, talks to other systems, and has to keep working reliably while people depend on it. That's engineering, not just design — and engineering is where the number comes from.

We build these, so treat the rest as informed but interested. The aim here is to help you scope the right thing and spend accordingly — not to talk you into the biggest tier.

What you're actually paying for

Before the tiers, it helps to know where the money goes — because it's rarely where people assume. A custom build is mostly:

• Discovery and scoping — working out precisely what it needs to do, for whom, and what happens in every edge case. Skipping this is how projects go wrong.
• Design — not just how it looks, but how it flows, so people can actually use it without training.
• Build — the engineering: the logic, the database, the security, the integrations with tools you already use.
• Testing — making sure it works under real conditions, with real (sometimes messy) data, before anyone relies on it.

The visible part — the screens — is the tip. Most of the cost is the machinery underneath that makes those screens trustworthy.

Tier 1 — a simple tool or MVP (~£10,000–£20,000)

A single, well-defined job: an internal tool that replaces a painful spreadsheet, a straightforward booking form with logic, a first version of a product to test with real users.

• What it is: one core workflow, built properly — the right foundation without the bells and whistles yet.
• Cost: roughly £10,000–£20,000 +VAT, staged across the project.
• Right for: a business with one specific, painful bottleneck to remove, or a founder testing a product idea before committing to the full thing.
• The catch: it's deliberately focused. Do the scoping honestly so "simple" doesn't quietly grow into "platform" halfway through — that's the classic budget-buster.

Tier 2 — a real portal or booking system (~£20,000–£40,000)

A proper system multiple people rely on: a client, member, investor or tenant portal; a booking and scheduling system with payments; an operational dashboard the team runs on.

• What it is: several connected workflows, user accounts and permissions, real data, and integrations with your existing tools — designed to be used every day.
• Cost: roughly £20,000–£40,000 +VAT, depending on the number of workflows, user types and integrations.
• Right for: an established business where the tool runs a real part of the operation — client access, bookings, internal process — and doing it badly costs money or reputation.
• The catch: this is the tier where scope discipline matters most. Every "could it also…" adds cost, so the value comes from building what genuinely earns its place first and adding the rest once it's proven.

Tier 3 — a full custom platform (£40,000+)

Bespoke software at scale: a platform that is a big part of how the business runs, with complex logic, many user types, deep integrations, and real reliability and security demands.

• What it is: genuine infrastructure — built, maintained and supported as an ongoing system, not a one-off deliverable.
• Cost: £40,000 and up, often into six figures for true scale, plus ongoing maintenance.
• Right for: businesses where the platform is central to how they operate or make money at scale, where downtime has a real cost, and where it must integrate, scale and stay secure under load.
• The catch: cost, complexity and a long-term commitment. Only the right call when the requirements genuinely demand it — never because it sounds ambitious.

What moves the price up or down

Two portals that sound identical can differ by tens of thousands. The things that actually move the number:

• Number of distinct workflows. One job is cheap; ten interconnected ones is a platform.
• User types and permissions. "Everyone sees everything" is simple. Admins, staff, clients and guests each seeing different things is more work — and usually necessary.
• Integrations. Every existing system it must talk to (payments, accounting, a CRM, a calendar) adds engineering and testing.
• Data complexity. Simple records are quick; intricate relationships, history and reporting are not.
• Reliability and security demands. The more that depends on it — and the more sensitive the data — the more rigour it needs, and rigour costs.
• How well it's scoped. The single biggest lever. A clear, disciplined spec keeps the price honest; a vague one lets it balloon.

The running costs to plan for

Unlike a brochure site, a custom app is a living system — budget for keeping it alive, not just building it:

• Hosting and infrastructure — a real app needs proper hosting; cost scales with usage.
• Maintenance and updates — security patches, dependency updates, small fixes. Non-negotiable for anything holding real data.
• Support — someone to call when something breaks or the business needs a change.
• Iteration — the good ones evolve. Budget for the improvements you'll want once people are using it.

A build you can afford to make but not to maintain is a false economy. Factor the running costs in from the start.

Is a custom build worth it?

The number is only ever justified by the return. A custom platform earns its cost when it does a measurable job — removes hours of manual work, opens a revenue stream, or takes real risk out of the operation. When we rebuilt the workflow properly for Training ByteSize, they saw a 65% improvement in manual admin-task efficiency — the kind of return that pays a build back rather than just adding a nice-to-have. That's what the custom platforms and portals we build are for: software that does a real job, built around how the business actually works.

The wrong reason to build is that it sounds impressive. The right reason is a number — saved hours, extra revenue, removed risk — that clearly outweighs the cost.

FAQ

How much does a custom web app cost in the UK in 2026?

Roughly: a focused tool or MVP £10,000–£20,000, a real portal or booking system £20,000–£40,000, and a full platform £40,000 and up — often six figures at true scale. Plus running costs (hosting, maintenance, support) on all of them. The number depends mostly on how many workflows, user types and integrations it needs.

Why is a web app more expensive than a website?

A website mostly displays information; an app does things — logins, data, rules, integrations, reliability. That's engineering rather than just design, and it has to keep working while people depend on it. There's simply more to build, secure and test.

How much does a booking system cost to build?

A straightforward custom booking form with logic sits around £10,000–£20,000; a full booking-and-scheduling system with payments, multiple user types and integrations is more like £20,000–£40,000. Off-the-shelf booking tools are cheaper to start with — build custom when your process is distinctive enough that the generic tools don't fit.

What are the ongoing costs of a custom platform?

Hosting and infrastructure, maintenance and security updates, support, and iteration as it evolves. A custom app is a living system, not a one-off — budget for keeping it running well, not just building it.

How long does it take to build a custom portal?

For a proper portal, typically 12–16 weeks from kickoff, depending on scope. A simpler single-workflow tool can be faster; a full platform longer. Honest, thorough scoping at the start is what keeps both the timeline and the budget under control.