How much does custom software cost in the UK?

Three shapes cover most of what UK businesses actually commission.

Those brackets sit where most UK agency pricing guides land, which is worth saying because it means a quote well outside them deserves a question. Anything materially cheaper is usually offshore, a smaller scope than you think you are buying, or a figure that will grow once the work starts.

There is no other mechanism. Whatever arrives on the quote, someone has estimated an amount of engineering effort and multiplied it by what their people cost. Everything that makes quotes hard to compare is a disagreement about one of those two numbers.

On the rate, the UK market splits by geography and seniority. Published agency rate cards tend to land in four bands: roughly £25 to £50 an hour for offshore teams with a UK front, £45 to £90 for London product engineering, £60 to £140 for boutique London agencies, and £120 upwards once you reach the large consultancies. We charge £100 an hour, which is £800 on an eight hour day, and it is the same number whether the work is a web app, a mobile app or an integration.

The rate on its own tells you very little, which is the part worth being careful about. A £400 day rate covering a team of two juniors, a mid-weight developer and a project manager can produce a larger invoice than a £800 rate covering one senior engineer who has built the same thing four times before. Ask how many people, at what level, for how many days. The blended figure hides the answer.

The second number, the day count, is where the real variance lives. A quote is only as good as somebody's estimate of how long each part takes, which is why we publish ours.

Three items go into every build we quote. None of them appears on a wishlist, because nobody wants them in the sense that they want a booking screen. Software does not work without them.

These are the bands we estimate from, in engineering days, before the multiplier for platform and scale. At £800 a day you can read the cost straight off them.

Where you land inside a band depends on volume and awkwardness. Stock control for a shop with forty product lines is a different job from stock control for a distributor with forty thousand, and the second one needs thinking about batches, locations and reservations that the first does not.

Two multipliers then apply. Building for mobile adds about 15 per cent over web alone, and building both adds about 30 per cent, because two front ends means two sets of testing and two release processes. Named integrations run one and a half to three days each, so connecting to Xero, Sage or Stripe is usually £1,200 to £2,400. An integration with something we have not seen before, or something with poor documentation, runs three to six days.

Four things routinely appear after the number a business has already budgeted for.

VAT. UK agency quotes are normally exclusive of it, so £12,000 on a £60,000 build, which matters a great deal if your business cannot reclaim it. Check which figure you are holding before it goes in front of a board.

Hosting and running costs. Between about £60 and £250 a month for a typical business system, depending on load and how much data you are keeping. Mobile adds the Apple Developer Program at 99 US dollars a year, and Google Play, which takes 25 US dollars once rather than annually. Small numbers, but the hosting is permanent, and a three-year view of a project should include it.

Support. Software needs someone to answer when something breaks, and that is a monthly arrangement rather than a line in the build. What good looks like is covered in our piece on what a proper support arrangement includes.

Getting your existing data in. Rarely quoted, frequently the messiest part of the project. Ten years of spreadsheets with inconsistent customer names take real effort to reconcile, and the work has to happen before anyone can use the new system. If you are replacing something that has been running for years, our legacy software development and support work exists for exactly this.

For a tool your own team uses, the price is answerable. Count the hours currently going into the process, cost them at what those people are paid, and compare. A system that gives eighteen hours a week back to staff on £30,000 is returning something in the region of £25,000 a year against a £45,000 build, which pays for itself inside two years and keeps going after that.

The returns that do not show up in that sum are often the ones that matter. One set of numbers rather than three systems disagreeing. An audit trail that exists whether or not somebody remembered to keep one. Work that carries on when the person who knows how it is done is away. Those are real and they are hard to put a figure against, so we leave them out of the payback maths and mention them separately.

For a customer-facing product the sum does not work, and anyone presenting you with a revenue projection for an app that does not exist yet is guessing. What you can sensibly ask is what the first release costs, how quickly it can be in front of real users, and what it costs to keep going while you find out whether it works. That is the case for building a mobile app or a web application in slices rather than commissioning the whole thing at once.

The expensive failures we get called into are rarely about the day rate. A build quoted at £25,000 that has to be redone costs more than one quoted at £45,000 that works.

Two patterns account for most of it. The first is scope that was never really agreed, where the brief said "a system to manage jobs" and everyone pictured something different until month three. The second is software built fast by someone who has since moved on, with no tests, no documentation and no way to deploy it. We see the second one weekly now that a great deal of code is written with AI assistance, and it is fixable, which is what our project rescue service is for.

The way to avoid both is unglamorous. Agree a first release small enough to be delivered in ten to fourteen weeks, get it in front of the people who will use it, and let what you learn shape what comes next. A project priced in slices is one you can stop, and the ability to stop is worth more than a discount.

Everything above is the general case. Putting your own answers through the software and app cost calculator takes about three minutes and gives you a costed build, a timeline, your integrations priced individually and, for an internal tool, a payback figure. It runs on the same bands set out above, so nothing is being held back for the sales call.

If part of what you are considering is handing a process to software rather than rebuilding it, the AI agent cost calculator answers that question instead, and what an AI agent costs a UK business covers the pricing in the same detail as this piece. Both tools sit on our free tools page.