How much does custom software cost in the UK? Seven firms, one measured day rate.

Search the question and the first page of results will tell you that custom software costs anything from £5,000 to £600,000. Every one of those pages is right about its own customers and wrong about yours. A Suffolk agency that builds booking systems for gyms, a Wiltshire consultancy that builds job costing tools for trades, and a Manchester firm that builds enterprise platforms are describing three different products under one name, and their floors and ceilings barely overlap.

So rather than add another opinion, we read every UK firm that publishes bespoke software prices in 2026, recorded each figure with its date, and put them in one table. Then we did what the other guides do not: we set the quoted day rates against the only measured figure that exists, the rate actually agreed on software developer contracts, tracked by IT Jobs Watch from live postings. That gap is the most useful number in this guide, because it lets you reverse any fixed quote into the days it implies.

Two things to hold on to as you read. All prices exclude VAT unless stated, and the smaller firms in the table are more likely to quote a figure that already includes design and testing, while the larger ones price those separately. And a day rate on its own tells you nothing; the day rate multiplied by the number of days nobody has written down is the price, and the number of days is the thing this guide gives you a way to check.

These are the firms whose own pages state prices, as read on 14 September 2026. The dates matter: four of the seven pages were written or updated in the last six months, which is why the smaller figures here are lower than guides from 2024 would suggest. Where a firm quotes a market range rather than its own price, that is what we recorded.

All figures exclude VAT. "Market" means the firm was describing the wider market rather than its own price. Read on the dates shown; prices change, and we will update the table when they do.

Reconciling seven sources is mostly a matter of noticing when two firms describe the same thing under different names. A "focused module" at SWF, a "focused tool" at Jabu and a "basic app" at Fulminous are one product. Once the labels are lined up, the market agrees on more than the headline spread suggests, and the outliers are explained by who each firm sells to.

Every guide in the table quotes day rates. IT Jobs Watch measures them, from the rates attached to live contract postings. In the six months to 14 September 2026 the median day rate for a software developer contract in the UK was £525, up 5 per cent on £500 a year earlier, across 431 postings. The tenth percentile was £365 and the ninetieth £613. London is barely different: a median of £529 across 83 postings, with a ninetieth percentile of £709.

Set that against the £800 to £1,200 a day that TotalSoft attributes to central London agencies, or Red Eagle’s £600 to £900 for an architect. The gap is not dishonesty. An agency day includes a project manager, a designer, testing, the office, and the margin that pays for the weeks between projects. But it means a fixed price from an agency implies fewer engineering days than the same price from a contractor, and you should know which you are buying.

The useful trick is to reverse it. Divide any fixed quote by the measured median of £525 and you get the number of contractor days it would buy. A £18,000 application is 34 days of one developer at market rate. If a quote for the same scope implies 80 days, either the scope is bigger than you think or the price is. Ask which.

A fixed price is a supplier’s estimate of days, multiplied by their rate, plus the contingency they carry for being wrong. Two of the seven firms publish how that total splits across the work, and their splits agree closely. Square Root puts discovery and technical planning at 5 to 10 per cent of the project, backend and frontend engineering at 40 to 60 per cent, and testing and compliance at 10 to 20 per cent, with design priced separately at £3,000 to £20,000. Fulminous puts discovery at 10 per cent, design 15, development 50, testing 10, deployment 5 and maintenance 10.

That means roughly half of any fixed price is engineers writing code, and the other half is the work that decides whether the code is right: discovery, design, testing and handover. A quote that is all engineering has skipped the half that prevents the expensive rebuild. It also means a quote can be sanity-checked line by line: on a £20,000 application, expect around £1,000 to £2,000 of discovery, £8,000 to £12,000 of engineering, and £2,000 to £4,000 of testing.

The reason fixed price is the better buy is not that it is cheaper. It is that the estimating risk sits with the party able to judge it. A day rate pays a supplier for being slow and transfers every mis-estimate to you, the party least able to judge whether the estimate was reasonable. The catch is that a fixed price only works when both sides accept a written list of what is not included, and many buyers find that document uncomfortable. It is protecting you more than it protects the supplier, because everything on it is a change you would otherwise have paid for twice.

Take a fourteen-person building services firm that quotes, schedules and invoices from spreadsheets and a shared inbox. It wants one application: office staff raise and price jobs, engineers see their day on a phone and log materials, customers open a link to approve a quote, and every invoice lands in Xero without rekeying. Three user types, one integration, one PDF generator, nothing that has to run unattended overnight. This is an illustration built from the published figures, not a client account.

Priced from days first. A plausible plan is three days of discovery, four of design, twenty-two of build, six for the Xero integration and quote approval flow, five of testing and two of handover: 42 days. At the measured median of £525 that is £22,050. At Red Eagle’s senior developer rate of £550 to £750 it is £23,100 to £31,500. At TotalSoft’s central London agency band of £800 to £1,200 it is £33,600 to £50,400 for the same days.

Now priced from the published bands. SWF’s own worked example of a job costing system is £18,000 over eight weeks, and its full-application band is £12,000 to £30,000. Red Eagle’s example of a property scheduler with a similar shape is £18,000 in six weeks. TotalSoft’s mid-market band with API integrations is £25,000 to £60,000. Augustova would price it as a business application at £10,000 to £20,000 fixed, or at the low end of a platform if the engineers’ phone view must be a store-published app. The spread from the cheapest credible number to the most expensive is roughly three to one, and every figure in it is defensible. What differs is the size of team, the amount of process, and where the risk sits.

The published guides agree on the drivers even where they disagree on the numbers, and the agreement is worth more than any single price band, because it tells you which questions a supplier will ask before quoting and which answers push the quote into the next band. These are the drivers that change a price by thousands rather than hundreds, in roughly the order of how much they move it, with the published figure that shows the size of the effect where one exists.

Two of the seven firms show their working on return, which is rarer than it should be. SWF’s example: two members of staff each spend four hours a week on a task the software removes, which is 400 hours a year, or about £10,000 of recoverable capacity, so a £15,000 system pays for itself in eighteen months. Jabu compares a fifteen-user SaaS stack at £1,400 to £1,800 a month, which is £84,000 to £108,000 over five years, against a £25,000 custom build plus £120 a month of hosting, which is £26,400 in year one and £32,000 over five years, or £51,200 with £400 a month of support. Break-even lands in month fifteen to twenty-four.

Both sums only work when the hours are real and measurable. The honest test before you commission anything is whether you can name the people, the task and the hours. If you cannot, buy the off-the-shelf tool for a year and count. The DSIT Business Data Survey 2026 found 31 per cent of UK businesses use a public cloud provider such as AWS, Azure or Google Cloud, which is roughly the share for whom a bespoke build is a realistic operational step rather than a first encounter with hosting.

Since we are one of the rows in the table, here is how Augustova answers its own questions. Bespoke software is £8,000 to £30,000 as a fixed price per phase, on a ladder of a single process at £4,000 to £10,000, a business application at £10,000 to £20,000, a startup MVP at £10,000 to £20,000, and a platform with mobile apps at £20,000 to £30,000 and up. Every phase has a written scope and an explicit list of exclusions; a new idea becomes a new phase rather than a delay. You own the code and the accounts from day one, and handover includes documentation, credentials, a runbook and a recorded walkthrough. We do not sell days, for the reasons the measured market makes obvious.

We searched Google UK for the question and its variants on 13 and 14 September 2026, read every UK software firm on the first pages that publishes bespoke software prices, and recorded each figure with its date. Where a firm gave a range for the wider market rather than its own price, we recorded it as such. We excluded pages that quote no figures and directories that aggregate unverifiable estimates. Consensus bands are the overlap of the majority of sources; the disagreement column records the outliers rather than hiding them.

Measured contract rates are IT Jobs Watch’s, from live UK postings in the six months to 14 September 2026. Cloud adoption is from the DSIT UK Business Data Survey 2026, with fieldwork from October 2025 to January 2026. The worked example is an illustration built from the published figures and a plausible day plan; it is not a client account. All prices exclude VAT. The date at the top of this page is the date of the last check, and we will revise the tables as the sources change.