Search “custom software development cost UK” and the honest answer is a very wide range: simple internal tools land around £10,000–£30,000, a standard business application runs £30,000–£80,000, a more complex platform sits at £70,000–£150,000, and enterprise-grade systems go from £150,000 upward past £500,000. Most B2B commissioning projects — the kind a founder or product lead is actually planning — fall in the £40,000–£150,000 band.
That’s a wide enough range to be useless on its own, so it’s worth being direct about what actually moves a project from one end to the other:
- Team composition, not headcount. A team of three mid-level developers in London runs roughly £1,800 a day. The single biggest cost lever is whether you’re paying for a large team working slowly or a smaller, senior team working fast — day-rate totals can look similar while delivery speed differs by months.
- Compliance load. GDPR obligations, and sector-specific requirements if you’re building anything touching healthcare, finance, or personal data, add real scoping and testing time that shows up in the quote, not as a separate line item.
- AI integration. Demand for AI features — not vibe-coded prototypes, but properly integrated AI product functionality — is now a standard line in 2026 scoping conversations and pushes budgets up versus a purely conventional build.
- What happens after launch. Ongoing maintenance, monitoring, security patching, and iteration typically run 15–25% of the original build cost per year. A £100,000 build usually means an additional £15,000–£25,000 annually to keep it running well — a number that’s easy to miss when comparing headline build quotes.
So what
If you’re trying to budget before you’ve scoped anything, the honest starting point is the mid-band — £40,000–£150,000 for most real business applications — and the variable to interrogate in any quote isn’t the headline number, it’s who’s actually doing the work and what the day rate implies about delivery timeline and seniority. Cheap quotes usually mean a larger, more junior team taking longer; expensive quotes should mean a smaller, senior team moving faster, not padding. If you want a straight answer on what your specific project would cost rather than a published range, that’s a conversation, not a calculator — see how we approach custom software development or get in touch to talk through your scope.