Custom software or off-the-shelf: how to decide

Declared bias before anything else: we are an AI consultancy and we build custom software. That makes this page the least likely place on the internet to find a fair answer, so every figure below comes from a vendor’s own published price list, read on 21 September 2026, and every assumption we add is labelled as ours.

At a glance

• Assume the product wins. It usually does, and the first section explains when it stops.
• Score one process, not the whole company. The answer is rarely the same for all of them.
• Three years of a typical 25-person UK stack, at the vendors’ own list prices, comes to about £94,000. That is close enough to a mid-sized build that the money alone will not decide it.
• The hybrid wins most often: keep the product, build the gap.
• Test the decision in one week, on one real job and one awkward exception, before you spend anything.

Why should you start by assuming off-the-shelf wins?

Because a good product is the cheapest way to get a defined process running, and most processes in most businesses are not unusual. Someone else has already built it, tested it against thousands of customers, and is selling it for less per month than a day of developer time.

A product also comes with things a build does not: a support line, a roadmap somebody else funds, security patching, an ecosystem of people who already know it, and the ability to stop paying. Those are real and they are undervalued in every comparison written by a supplier of custom work.

So the burden of proof sits with the build. The question is never “would custom be better”, because custom is almost always better in isolation. The question is whether it is better by enough to justify the difference, for this process, for three years.

What are the four ways a good product stops fitting?

It is rarely a sudden failure. It is four specific frictions, and you can name which one you have.

The spreadsheet appears beside it. Somebody keeps a separate sheet because the product cannot hold something the business needs. That sheet is the shape of the gap, and it is the single most reliable signal in this whole exercise.

The reporting stops answering the question. The data is in there, and getting the view a director wants requires an export and half a day. This is the most common reason a business says it has outgrown a system, and often the cheapest to fix without replacing anything.

The exception path escapes the software. The routine jobs run inside the product and the awkward ones run by email. Over time the awkward ones get more valuable, and the system of record stops recording the money.

Per-seat pricing outgrows the value. You are paying full price for people who only need to look at one number once a week. This is a pricing mismatch, not a functional one, and it is worth naming as such before commissioning anything.

How do you score one process rather than the whole company?

Pick one process. Not the department, not the company. A month-end close, a new-starter onboarding, a supplier approval, a monthly reconciliation. Score these eight, one to five, and write the reason beside each.

1. Fit today. How much of this process does the product already handle without a workaround?
2. Workaround cost. How many hours a month go into the spreadsheet, the re-keying and the chasing that the product caused?
3. Exception rate. What share of cases leaves the software entirely?
4. Reporting gap. Can a director get the view they need without an export?
5. Seat economics. How many licences are paying full price for light use?
6. Rate of change. How often does this process change? High scores here argue for the product, not the build.
7. Data ownership. If you left the vendor tomorrow, what would you get back, including history and attachments?
8. Distinctiveness. Is the way you do this a real reason customers choose you, or is it just how it ended up?

A high total on two, three and eight argues for building. A high score on six argues loudly against it: you would be paying to set concrete around something still moving. And if the only high score is five, you have a procurement problem, not a software problem, and the cheapest fix is a conversation with your account manager.

What does three years of seats cost against one build?

Here is the sum most comparison pages skip, done properly. Every unit price is the vendor’s own published UK list price, read today and linked below. The seat counts are our assumption for a 25-person business and are stated so you can change them.

Line	Published list price	Assumed use	36-month cost
Salesforce Sales Cloud, Core edition	£156 per user per month, billed annually	15 users	£84,240
Monday.com, Basic	£8 per seat per month, billed annually	25 seats	£7,200
Xero Ultimate	£70 per month after the introductory period	1 subscription	£2,520
Three-year total			£93,960

Now the other side, using published UK build bands rather than a quote from us. Make It Simple publishes small bespoke systems at £20,000 to £60,000, and Unity Bridge publishes a focused custom CRM at £20,000 to £50,000 over two to four months. Take the middle at £45,000. Add hosting at the £200 to £2,000 a month that Square Root publishes, say £400. Add maintenance at Square Root’s 15 to 25 per cent of build cost a year, say 20 per cent, which is £9,000. Three-year total: £45,000 plus £14,400 plus £27,000, or £86,400.

The fair conclusion is that those two numbers are close, and anybody who tells you the arithmetic clearly favours one route has chosen convenient assumptions. What moves it is not the headline: it is whether the build really removes the licences, whether the seat count grows, and whether the process changes. Run it with your own numbers, and if the two totals land within twenty per cent of each other, stop using cost as the deciding factor and use the eight-factor score instead.

One caution about the build column: a build does not remove your accounting package or your email. Most builds replace one licence, not the stack.

The hybrid that usually wins: keep the core, build the gap

In a business of £1m to £50m turnover, the right answer is usually neither pure route. It is to keep the product as the system of record, and build the specific piece that does not fit around it.

Side by side

Three routes for one process, three years out

Score one process, not the company. The money lands close, so it rarely decides on its own.

	Keep the productAs sold, seats and all	Build it allCustom from the ground up	Keep the core, build the gapThe hybrid
What it looks like	example-crm-seats.xlsxSheet ItemPer year3 years 25 seats£31,320£93,960 Flagged: Exceptions: still email and sheetsFlagged	example-build-quote.xlsxSheet ItemThree years Custom build£86,400 Flagged: Support and patching: yours to fundFlagged Matched: Handles every exceptionMatched	What to build, what to keep2 of 3 Done: Keep: contacts, pipeline, support and patching Done: Build: the approval step and its exceptions To do: Rebuild the whole product: not needed
Three years, at list prices	£93,960 for a 25-person stack	£86,400 at a mid-band build	A small, bounded build
Support, patching, roadmap	In its favour: Someone else funds it	Against it: Yours to fund	In its favour: The product keeps them
The awkward exceptions	Against it: Escape to email and sheets	In its favour: Built in	In its favour: The gap is built for them
If the process keeps moving	In its favour: The vendor adapts	Against it: Concrete around it	Mixed: Only the small piece moves
The verdict	Assume this wins until a friction appears	When workarounds, exceptions and distinctiveness all score high	Usually right at £1m to £50m turnover

in its favour mixed against it

That might be a proposal builder that reads from the CRM and writes back. A month-end pack that pulls from the accounts package and the stock system. A view for the people who only need to look, so you stop buying full seats for them. Each of those is a small, bounded build with a clear stopping point, and each leaves the product doing what it is good at.

The hybrid is proposed less often than it should be, and the reason is commercial: it is the smallest sale available to a supplier of custom software. It is also usually the best one, which is why we lead with it.

How do you test it before spending anything?

Run one week of work through the question before you commission anything. It costs nothing but attention and it settles most arguments.

Choose one representative job. Not the biggest, not the worst. A normal Tuesday.

Include one awkward exception. Pick a case from the last month that did not follow the process. The exceptions are where the real requirement lives.

Follow the data all the way through. Where does each field come from, who types it, and how many times is the same fact entered? Count the re-keying.

Price the missing work. The hours in the spreadsheet, the chasing, the corrections. Use a loaded hourly cost and state it.

Test the custom option too. Describe what would have to exist for this job to run without the workaround, in one paragraph. If you cannot write that paragraph, you are not ready to commission a build.

A system we run ourselves

Most of what a mid-sized business builds is a bounded system for one department, and our own business is the example we can open. We run a custom CRM rather than a licensed one, an autoposter that keeps the platform’s receipt for every post, and outreach engines, each built for a gap that off-the-shelf software did not fit.

The claim is deliberately narrow. It shows that a custom system can run in daily use to an auditable standard. It does not prove that a build beats a product for your process, and we do not say it does. What we cannot show you yet is stated plainly on our evidence page.

The same test works for the bounded builds that matter in other departments. A month-end pack should show where each figure came from. A new-starter checklist should show who did each step and when. A supplier approval should show the rule that approved it. If a figure cannot be traced back to its source, the build has only moved the spreadsheet.

When is custom the wrong answer, including for us?

When your objection to the product is the subscription fee. Building to avoid a licence is almost always the more expensive way to avoid it.

When the process changes every few months. Products absorb change on somebody else’s budget; builds absorb it on yours.

When nobody internally owns the process. Custom software makes a defined process faster. It does not create the definition, and a build commissioned into a vacuum becomes an expensive version of the old confusion.

When you cannot say what “working” looks like in a sentence with a number in it. If success is not measurable, neither is completion, and neither is the argument about whether the supplier finished.

And when the plain answer is that the product would fit if two people agreed on a process. That is a management decision worth having before a procurement one.

What does it cost to find out?

The 30-minute fit call is free and nothing is purchased on it. If the process warrants a proper read, the AI Constraint Audit is a fixed £2,000 over fourteen days. It finds constraints, weak points and opportunities to save or earn serious money, and it ends in four documents you own: a constraint map, an opportunity map, economic cases and a ranked next step. A more extensive audit always follows, and it is included in any build proposal. Those documents are portable. You can take them to another supplier and get a comparable quote, which is the test of whether an audit was real.

The audit fee is not credited against a build. That is what allows the recommendation to be “keep what you have”. The systems we build, and what we will and will not take on, are described on custom process systems, and the wider service is under custom builds.

What this does not apply to

This is written for UK businesses of roughly £1m to £50m turnover with an operations director, a contracts manager or a finance lead who owns the process in question. It assumes you already run some software and are deciding what to do about the parts that do not fit.

It does not apply to sole traders or very small teams, for whom the product is almost always the answer. It does not cover regulated core systems in financial services or healthcare, where replacement carries approval requirements outside the scope of this page. It does not cover public-sector procurement. And the three-year sum above is an illustration built on stated assumptions, not a quote for anyone.

When we are the wrong choice

If the product fits and the objection is price, we will tell you to negotiate rather than build, and that conversation is free.

If you want the whole company rebuilt at once, we are the wrong supplier. We would propose the smallest useful first version, and some buyers find that underwhelming.

If you need it working next month, a build is the wrong shape and a hybrid or a product is not a compromise, it is the correct answer.

If nobody can be named as the owner of the process, no supplier can fix that.

Sources

Read on 21 September 2026.

• Salesforce UK, Sales Cloud pricing. Starter Suite £20, Pro Suite £80, Core £156, Advanced £316 and Max £440 per user per month, billed annually.
• Monday.com pricing. Basic £8 per seat per month billed annually.
• Xero UK pricing plans. Ultimate £70 a month and Comprehensive £55 a month after the introductory period.
• Make IT Simple, bespoke software cost UK. Small bespoke tool £20,000 to £60,000; mid-range platform £60,000 to £200,000; complex £200,000 to £600,000 and above.
• Unity Bridge Solutions, custom CRM development UK. Focused CRM £20,000 to £50,000 over two to four months.
• Square Root, cost to develop software in the UK. Maintenance and support 15 to 25 per cent annually; cloud infrastructure £200 to £2,000 a month.
• Jabu Designs, how much does bespoke software cost. A five-year comparison of a SaaS stack at £1,400 to £1,800 a month against a £25,000 build, reaching £84,000 to £108,000 versus about £32,000. Their assumptions, not ours, and worth reading beside our sum above.
• Orbn, custom software vs off-the-shelf. The clearest competing decision framework on this question, with a named customer and £4,500 and £36,000 on the page. Those figures are asserted and link to nothing, which is the reason ours link to list prices.

Related reading

• How much does custom software cost in the UK?
• You have outgrown your CRM. Rebuild, replace or extend?
• What business process automation costs in the UK