---
title: "What custom software costs to run: the real numbers (UK, 2026)"
description: "What bespoke software costs to run in the UK: about £800 a year for a version one at list prices, nothing per seat, against the 15 to 25 per cent rule."
canonical: https://www.clientflow.ai/guides/running-costs
category: Cost
authors: ["Sohail Chowdhary"]
published: 2026-09-05
verified: 2026-09-05
language: en-GB
---

# What the software you own actually costs to run

The itemised bill for a version one, in your name and at list prices, what grows with use and what never does, and where the “15 to 25 per cent a year” rule came from.

By Sohail Chowdhary · Published 5 September 2026 · Verified 5 September 2026 · 13 min read

**Summary:** A version one of a bespoke system costs about £800 a year to run at list prices: hosting, a database with sign-in, transactional email and error monitoring, every account in your name and none of it per seat. Over three years that is about £2,600 including the ICO fee, against the £2,700 to £4,500 a year the industry rule of thumb would predict for an £18,000 build. The rule comes from studies of large, long-lived systems in which three quarters of what was counted as maintenance was new features, which is work we scope and price separately. Support after launch is a fixed monthly fee and optional; ending it changes nothing about the software.

## Contents

1. [The short answer](https://www.clientflow.ai/guides/running-costs#the-short-answer)
2. [The bill, itemised](https://www.clientflow.ai/guides/running-costs#the-bill)
3. [What grows with use, and what never does](https://www.clientflow.ai/guides/running-costs#what-grows)
4. [Three years, added up](https://www.clientflow.ai/guides/running-costs#three-years)
5. [What maintenance actually is, on this stack](https://www.clientflow.ai/guides/running-costs#what-maintenance-is)
6. [Where the 15 to 25 per cent rule came from](https://www.clientflow.ai/guides/running-costs#the-rule)
7. [The costs people forget](https://www.clientflow.ai/guides/running-costs#the-costs-people-forget)
8. [Questions people ask about running costs](https://www.clientflow.ai/guides/running-costs#questions)

## 1. The short answer

Bespoke software runs on the same managed services a software product runs on. The difference is that the accounts are in your name and the bill is for usage, not for seats. At version-one scale that bill is about **£800 a year** at list prices, and it stays there until the system is genuinely busy.

- **The services, a month**: $91 a month (Hosting, database and sign-in, email and monitoring, at list price[^1][^2][^3][^4])
- **Three years, web only, about**: £2,600 (Services, domain and the ICO fee, with no support fee, converted at £1 = $1.35[^7])
- **Of an £18,000 build, a year**: 4.8% (Services and the ICO fee against the first-band example in the own or rent guide)

That is the whole of the compulsory bill. Two things sit outside it by choice: support after launch, which is a fixed monthly fee scoped with the build and optional, and new features, which are always scoped and priced before the work. The rest of this guide is the itemised list, what changes as you grow, and why the number is so far below the rule everyone quotes.

## 2. The bill, itemised

Every line below is a service you can look up, at the price on the vendor’s own page on the date shown. Every account is opened in your name from the first week and you pay the provider directly, so nothing is routed through us or marked up. If we disappeared tomorrow, the invoices would not change.

| Service | What it does | List price |
| --- | --- | ---: |
| Hosting[^1] | Serves the application worldwide, with a preview of every change and certificates renewed for you | $20 a month per developer seat |
| Database and sign-in[^2] | Your data and your users, in the London region, backed up daily | $25 a month |
| Transactional email[^3] | The emails the system sends: invites, status changes, receipts | $20 a month for 50,000 emails |
| Error monitoring[^4] | Tells whoever maintains it before a user does | $26 a month |
| Domain and DNS | Your address | A few pounds a year |
| Apple Developer Program[^5] | Only for an iOS app | $99 a year |
| Google Play[^6] | Only for an Android app | $25, once |

List prices, in the currency the vendor shows. The first four lines are the $91 a month above; the last two apply only if there is a phone app.

Payment processing is not on the list because it is a percentage of what you take, set by the provider, and it is the same whether the software is bespoke or bought. A support fee is not on it because it is a decision, and it has its own section below.

## 3. What grows with use, and what never does

Nothing on the list is priced per seat. A portal with two hundred client logins costs the same to run as one with twenty, and the same again at two thousand. What the services meter instead is real use: active users, data stored, traffic served, emails sent and errors recorded, each with an allowance that a version one rarely reaches.

- **Active users**: The database plan includes 100,000 monthly active users, then $0.00325 for each one beyond that[^2]. A system with five thousand users is a twentieth of the way to paying more.
- **Data and files**: 8 GB of database disk and 100 GB of file storage are included, then $0.125 and $0.0213 a gigabyte a month[^2]. Three years of a professional-services firm’s documents fit comfortably in the allowance.
- **Traffic**: Hosting includes 1 TB of data transfer a month, then from $0.15 a gigabyte[^1]. A business application does not approach that; a public site with video might.
- **Email**: 50,000 emails a month on the $20 plan, 100,000 for $35, and the next tier starts at $90[^3]. A notification-driven system sends a few thousand.
- **Errors**: 50,000 recorded errors a month on the $26 plan[^4]. A healthy system records a handful; a noisy one is a bug to fix, not a bill to pay.

The one line that does scale with people is hosting, at $20 a month per **developer** seat[^1]: the people who deploy the software, not the people who use it. A version one has one, and it can be yours.

## 4. Three years, added up

Here is the same list over the period most people plan on, converted at the European Central Bank reference rate the cost guide uses, £1 to $1.35[^7], and rounded. The build is the own or rent guide’s example, a first-band system at £18,000, so the two guides describe one purchase.

| Item | A year | Three years |
| --- | ---: | ---: |
| Services: hosting, database, email, monitoring[^1][^2][^3][^4] | £809 | £2,427 |
| Domain and DNS | A few pounds | About £30 |
| ICO data protection fee[^8] | £52 | £156 |
| Apple Developer Program, only with an iOS app[^5] | £73 | £220 |
| Google Play, only with an Android app[^6] | £19, once | £19 |
| Support after launch | A fixed monthly fee, scoped with the build, optional |  |
| **Total, web only, no support** | **About £860** | **About £2,600** |

The ICO fee is tier 1, which covers most organisations with ten or fewer staff; tier 2 is £78[^8]. The Apple and Google lines are added only if the build ships a phone app.

- Rule of thumb, 25 per cent of the build: £4,500
- Rule of thumb, 15 per cent of the build: £2,700
- The services bill: £809

**Fig. 1.** A year of running an £18,000 first-band build: what the industry rule of thumb predicts, against the services bill at list prices.

The gap is not an accounting trick. It is the difference between a rule written for one kind of system and a bill from another, and the next two sections explain each side of it.

## 5. What maintenance actually is, on this stack

Software does not wear out, but everything around it moves: the browsers people use, the phones they carry, the libraries the code is built from, and the security advisories that arrive for those libraries. Maintenance is keeping pace with that movement, and on a standard, managed stack it is a short and regular list.

- **Security updates**: The libraries a system depends on publish fixes continually. Applying them is routine work, a few times a quarter, and skipping it is how an owned system quietly becomes a liability.
- **One framework version a year**: Next.js has shipped a major version each October since 2022[^14]. Moving up is a planned job once a year, not a rebuild, and the years in between are quiet.
- **The services underneath**: Database engine versions, hosting runtimes and email providers change on their own schedules. On managed services most of that is done for you; the rest is a settings change with a test.
- **Backups and the restore drill**: The database plan takes a daily backup and keeps seven days[^2]. The work is not the backup; it is restoring one on purpose, once, so the day it matters is not the first time.
- **Monitoring**: Error monitoring reports the problem before a user does[^4]. Someone has to read the report; that is the part of maintenance that is a person, not a service.

Who does this is your choice, and the stack is chosen so the choice is real: Next.js, TypeScript, Supabase, PostgreSQL and Vercel are widely used and widely taught. Your own developer can do it, any developer you hire can do it, or our support does it for a fixed monthly fee scoped with the build.

> **The number that is not on this page**
>
> The support fee is not published, because it is scoped with the build rather than set as a percentage of it. Every build ships with a warranty window in which anything that does not do what the specification says is fixed at no cost. After that, support covers updates, the services underneath, monitoring and someone to call, never new features. Ending it changes nothing: you own the code and the accounts.

## 6. Where the 15 to 25 per cent rule came from

Ask most agencies what software costs to maintain and you will hear a percentage of the build: “between 15% and 25% of the original development cost annually”[^12], or “15% to 25% of the original development budget”[^13]. Neither page names where the figure comes from. The nearest thing to a source is a body of research on what maintenance costs over the whole life of large systems.

| Study | Year | Finding |
| --- | ---: | --- |
| Zelkowitz and others[^11] | 1979 | 67% of total software costs were maintenance |
| Lientz and Swanson, 487 organisations[^11] | 1981 | Over half of staff time was spent on maintenance |
| McKee[^11] | 1984 | 65 to 75% of software engineering effort |
| Port; Huff[^11] | 1988, 1990 | 60 to 70% of management information systems budgets |
| Eastwood, Fortune 1000 companies[^11] | 1993 | 75% of the information systems budget |
| Moad; Erlikh[^11] | 1990, 2000 | Over 90% of software cost devoted to maintenance and evolution |

As collected by Jussi Koskinen, Software Maintenance Costs, University of Eastern Finland, 30 April 2015[^11].

Those figures are real, and they describe something specific: large systems, kept for decades, inside organisations with their own engineering departments. Spread over a long life, a build that cost a year’s budget and then cost that again several times over does come out near a fifth of the build every year. The rule of thumb is a rounding of that.

The part that gets lost is what those studies counted. Lientz and Swanson found about 65% of maintenance was perfective, meaning improvements, and later work put enhancements at about three quarters of all maintenance cost[^11]. In other words, most of what the rule calls maintenance is new features. On a Clientflow build, new features are scoped and priced before the work, and they are never in the running cost.

### When the rule is right

1. The system is large, has many integrations that shift underneath it, and is genuinely being extended every month. Then the rule is describing a development budget, and it should be called one.
2. It runs on servers you operate rather than on managed services, so patching, backups, certificates and capacity are your labour.
3. It was built on an in-house framework or an unusual stack, so every change needs the people who built it.
4. It sits inside a regulated change process where every release needs testing, sign-off and documentation, and the labour of that process is the cost.

None of those describes a version one on a standard stack in your own accounts, which is why the bill on this page and the rule everyone quotes are both true, about different things.

If a supplier quotes you a percentage of the build, ask what they counted. The honest answer is usually a retainer for new features, and that is worth paying for on its own terms rather than as a fee for keeping the lights on.

## 7. The costs people forget

The services bill is the predictable part. Three other items belong in the plan, and one of them is not money.

- **The ICO fee**: Almost every UK organisation that processes personal data pays it yearly: £52 or £78 for most, £3,763 for the largest[^8]. It is owed whether the software is bespoke or bought, and it is often the line that surprises a first-time buyer.
- **Certification, if a customer asks**: Cyber Essentials starts at £320 plus VAT by organisation size[^9], and a penetration test before launch for anything holding payment, health or sensitive data runs from about £3,750 for a web application[^10]. Neither is a running cost of the software; both are costs of the business that runs it.
- **Someone who owns the accounts**: The accounts are in your name, which means someone in your business holds the logins, sees the invoices and decides. That is an hour a quarter, and it is the cost that stops a system becoming the one nobody can get into.
- **Not maintaining it**: The most expensive running cost is the one that was skipped. A system nobody updates keeps working for a year or two, and then a library it depends on has a published vulnerability and nobody has the context to fix it quickly. Budget the few hours a quarter, or the support fee, and it never arrives.

> **When running costs are the reason not to build**
>
> If there is nobody in the business who will hold the accounts, read the monitoring and make the call on updates, and you would rather not pay a support fee either, then a product with a vendor behind it is the better answer, and we will say so on the blueprint call. Owning software is cheap to run and it is not free to own.

**Want the running cost for your system, itemised?** Twenty minutes with the team who would scope the build. It ends in a firm range for the build and the list of services it would run on, or in the advice not to build.

[Apply for a blueprint call](https://www.clientflow.ai/apply)

## 8. Questions people ask about running costs

### How much does it cost to maintain custom software in the UK?

For a version one on a standard managed stack, the compulsory bill is the services: about £800 a year at list prices for hosting, a database with sign-in, transactional email and error monitoring, plus the ICO data protection fee of £52 or £78[^8]. Support after launch is optional and a fixed monthly fee scoped with the build. New features are scoped and priced separately, and they are where the industry’s larger percentages actually come from.

### Is the 15 to 20 per cent a year maintenance rule true?

It is a rounding of real research on large, long-lived systems, in which maintenance was 50 to 90 per cent of lifetime cost and about three quarters of that was enhancements[^11]. So it is true of a big system that keeps being extended, and it counts new features as maintenance. For a version one on managed services, the running bill is under five per cent of the build a year, and new features are a separate, scoped decision.

### Do we need a maintenance contract?

No. Every build ships with a warranty window, and after it you can maintain the software with your own developer, with any developer you hire, or with our support for a fixed monthly fee. The stack is standard on purpose so that all three are real options. What you do need is someone who applies security updates a few times a quarter and reads the monitoring, whoever that is.

### What happens if we stop paying for support?

Nothing happens to the software. The code is in a repository in your name, the hosting and database accounts are in your name, and the intellectual property is assigned to you under the agreement, so the system keeps running in your accounts and any developer can pick it up. What stops is the updates and the person to call, which is why the decision is about who does that work, not whether the software survives.

### How much does it cost to host a web app?

For a business application at list prices, about $20 a month for hosting per developer seat[^1] and $25 a month for the database with sign-in[^2], which is roughly £35 a month at today’s rate[^7]. Both include allowances a version one rarely reaches: 1 TB of data transfer a month on the hosting and 100,000 monthly active users on the database. Neither charges for the people who use the system.

### Who pays the hosting and database bills?

You do, directly, to each provider, from accounts opened in your name in the first week of the build. Nothing is routed through Clientflow or marked up, which means the invoices are the vendors’ list prices and they do not change if we are no longer involved. It also means you can see every line, cancel any of them, and give a new developer access without asking us.

### Can our own IT team maintain it?

Yes, and that is a deliberate property of the build. The stack is Next.js, TypeScript, Supabase, PostgreSQL and Vercel, all widely used and documented, with no in-house framework. The work is applying library updates, moving up one framework version a year[^14], keeping an eye on the monitoring and running a restore from backup once so the process is known. Handover includes the documentation and a training session for whoever will do it.

### What does it cost to run a mobile app on top?

The same services, plus the store fees: $99 a year for the Apple Developer Program[^5] and $25 once for Google Play[^6], paid by you to Apple and Google from accounts in your name. The maintenance side is a little heavier, because each year’s phones and operating systems have to be tested against, and app store reviews are on the stores’ timetable rather than yours.

## Sources

Every third-party figure above was read from the page cited, on the date shown. Vendors change prices without notice, so the date is part of the fact.

[^1]: [Vercel pricing](https://vercel.com/pricing). Pro, $20 a month per developer seat with $20 of usage credit; fast data transfer 1 TB a month included, then from $0.15 a gigabyte. Seen 5 September 2026.
[^2]: [Supabase pricing](https://supabase.com/pricing). Pro, $25 a month: 100,000 monthly active users then $0.00325 each, 8 GB disk then $0.125 a gigabyte, 100 GB file storage then $0.0213, 250 GB egress, daily backups kept seven days, $10 a month of compute credit. Seen 5 September 2026.
[^3]: [Resend pricing](https://resend.com/pricing). Pro, $20 a month for 50,000 emails or $35 for 100,000; Scale from $90 a month. Seen 5 September 2026.
[^4]: [Sentry pricing](https://sentry.io/pricing/). Team, $26 a month on annual billing for 50,000 errors; Business $80. Seen 5 September 2026.
[^5]: [Apple Developer, Program enrolment](https://developer.apple.com/support/purchase-activation/). 99 US dollars a year, charged in local currency. Seen 4 September 2026.
[^6]: [Google Play Console help, registering for a developer account](https://support.google.com/googleplay/android-developer/answer/6112435). A one-time $25 registration fee. Seen 4 September 2026.
[^7]: [European Central Bank, euro foreign exchange reference rates, 3 September 2026](https://www.ecb.europa.eu/stats/policy_and_exchange_rates/euro_reference_exchange_rates/html/index.en.html). USD 1.1615 and GBP 0.86055 to the euro, which makes £1 about $1.35. Seen 4 September 2026.
[^8]: [Information Commissioner’s Office, guide to the data protection fee](https://ico.org.uk/for-organisations/data-protection-fee/data-protection-fee/). Tier 1 £52, tier 2 £78, tier 3 £3,763, with £5 off by direct debit. Seen 4 September 2026.
[^9]: [National Cyber Security Centre, Cyber Essentials overview](https://www.ncsc.gov.uk/cyberessentials/overview). Certification priced by organisation size, starting at £320 plus VAT. Seen 4 September 2026.
[^10]: [Precursor Security, penetration testing cost guide, 2026](https://www.precursorsecurity.com/services/offensive-security/penetration-testing/cost). Web application tests from £3,750 over three to five days. Seen 4 September 2026.
[^11]: [Jussi Koskinen, Software Maintenance Costs, University of Eastern Finland, 30 April 2015](https://ocw.unican.es/pluginfile.php/2171/course/section/2000/SMCOSTS.pdf). A collection of empirical figures: Lientz and Swanson 1981, over half of staff time in 487 organisations; Zelkowitz 1979, 67%; McKee 1984, 65 to 75%; Port 1988 and Huff 1990, 60 to 70%; Eastwood 1993, 75%; Moad 1990 and Erlikh 2000, over 90%; about 65% of maintenance perfective and about 75% of its cost enhancements. Seen 5 September 2026.
[^12]: [Appinventiv, software maintenance cost guide, 20 November 2025](https://appinventiv.com/blog/software-maintenance-cost/). “Between 15% and 25% of the original development cost annually”, with no source given. Seen 5 September 2026.
[^13]: [Adevs, software maintenance costs 2026, 15 March 2026](https://adevs.com/blog/software-maintenance-costs/). “15% to 25% of the original development budget”, attributed to IEEE research without a citation. Seen 5 September 2026.
[^14]: [Next.js blog, release announcements](https://nextjs.org/blog). Next.js 13 on 25 October 2022, 14 on 26 October 2023, 15 on 21 October 2024, 16 on 21 October 2025. Seen 5 September 2026.

## About the author

**Sohail Chowdhary**, Co-founder and technical lead, Clientflow. Sohail leads product and engineering at Clientflow: the architecture, the backend and the code that ships. [LinkedIn](https://www.linkedin.com/in/sohail-chowdhary-23084289/)

## More guides

- [What bespoke software actually costs in the UK](https://www.clientflow.ai/guides/bespoke-software-development-cost-uk): From £10,000. The bands, the five things that move the number, and when not to build.
- [Own it or rent it? What the software you already pay for really costs](https://www.clientflow.ai/guides/build-or-buy-software-uk): £73,800 rented against about £20,400 owned, for a team of twenty over three years.

All guides: https://www.clientflow.ai/guides. Every guide is also served as Markdown at its URL with .md appended.