What custom software costs in the UK

Most firms in this market will not give you a number until you have had two calls. That is a sales technique rather than a technical necessity, and it costs you two hours to find out something a page could have told you in thirty seconds.

What follows is the published UK market position, where our own prices sit inside it, and the questions that separate a quote worth taking seriously from one written to win the work.

The bands, as the UK market publishes them

Day rates give you the other view of the same market. UK contract and agency rates in 2026 run roughly £250 to £350 for a junior developer, £400 to £550 mid-level, £600 to £800 senior, and £750 to £1,200 for a solutions architect. Regional agencies bill £350 to £550 a day and London teams £600 to £900. Agencies typically mark up an individual developer cost by 40 to 60 per cent to cover management, testing and overhead.

That arithmetic is worth doing on any fixed price you receive. A £30,000 quote implies somewhere around 40 to 60 working days. If the scope in front of you clearly needs more than that, the number is not real and the conversation about scope changes has already been scheduled by somebody.

The four things that actually move the number

• How many systems it has to touch. A tool that stands alone is straightforward. One that reads from your accounting system, writes to your CRM and stays correct when either of them changes is a different job. Integration is usually the largest single line.
• How messy the existing data is. Cleaning inconsistent records is frequently the longest part of a migration, and it can only be estimated properly after somebody has looked at the data. Any supplier who prices it confidently before seeing it is guessing.
• How many people use it, and how differently. One role doing one job is cheap. Five roles with different permissions, approvals and views is not.
• Whether anyone is regulated. Audit trails, retention rules and access controls add real work. They are also the reason the software gets signed off, so they are rarely worth cutting.

Where the money goes inside a project

What you pay after launch

The build price is not the cost of ownership, and a comparison that stops at the build price is incomplete. Budget for four things.

• Hosting. A business system for a few dozen users runs at roughly £20 to £200 a month, depending on how much data it holds and whether it has to stay fast at month end.
• Third-party licences. Anything the system connects to may charge for the connection, or only offer it on a higher tier. Bill these to yourself directly and own the accounts.
• Support. The long-standing industry benchmark for software maintenance is 15 to 25 per cent of the original build cost per year. Systems with many external integrations sit at the top of that range, self-contained ones at the bottom. Our own retainers start at 750 pounds a month, and software maintenance and support covers what that money buys.
• Change. Businesses move and software follows. Budget for it annually rather than treating each change as an unplanned cost.

Across a system’s full life, maintenance usually costs more than the original build. Research in software engineering has put roughly 60 per cent of total lifecycle cost in the maintenance phase against 40 per cent in initial development. That is not an argument against building. It is an argument for knowing the number before you start.

Six questions that tell you whether a quote is serious

1. 1What exactly is in scope, in writing, and what happens to anything outside it? A fixed price with no written scope is not a fixed price.
2. 2Who owns the finished system, everything needed to run and change it, and the logins at the end? If the answer involves continuing to pay them to hold it, that is a licence, not a build.
3. 3What have you assumed about our data? A supplier who has not asked to see it has priced a guess.
4. 4What is the payment schedule tied to? Milestones tied to delivered functionality beat milestones tied to dates.
5. 5If this runs over, who pays? The answer should be that they absorb their own estimating errors and quote separately for scope changes you request.
6. 6What does support cost afterwards, and is it optional? A build that only works with their retainer is a subscription wearing a capital cost.

When the honest answer is do not build

Below about £10,000 the cost of specifying, testing and documenting custom work tends to outweigh what you get, and an off-the-shelf product is usually the better purchase. Most published UK entry bands start around £15,000, and established studios rarely take on work below £10,000.

Building earns its cost in three situations. When the process is genuinely yours and is a reason clients choose you. When products get part of the way and the gap is the part that matters. When the work needed to bend a product into shape costs more than building something that already fits. Outside those three, buy something, and the build or buy guide is the longer version of that argument.