System integration cost is the number nobody quotes you upfront. The CRM has a monthly price on its website, the accounting platform has another, and the warehouse system has a third — but the price of making them talk to each other appears nowhere, because it depends on your systems, your data and your volumes rather than on a rate card. Ask three suppliers and you will get a connector subscription, a five-figure project quote and a shrug, all for the same four systems.
This guide puts real UK numbers on that gap. It builds on our detailed guide to API integration cost, which prices a single integration project from discovery to maintenance. Here the question is wider: what does it cost to connect the set of business systems a typical UK company runs — website, CRM, accounting, stock, payroll — and how do you keep the total system integration cost defensible as the set grows?
We cover the arithmetic that makes system integration cost grow faster than system count, realistic prices for the common system pairs, the three build routes and what each really costs in sterling, a worked example for a 25-person firm, and the recurring bill that follows go-live.
Every figure is either a published UK price, a rate from a named salary index, or arithmetic shown in full — and where a number is an assumption, it is labelled as one. By the end you should be able to build your own system integration cost estimate in an afternoon and recognise a padded quote on sight.
Table of contents
- What System Integration Cost Covers When You Connect Business Systems
- The Arithmetic: Why System Integration Cost Grows Faster Than Your Systems
- System Integration Cost by System Pair
- Three Routes to Connect Business Systems — and What Each Really Costs
- What the Integration Platforms Cost in Sterling
- The People Behind the System Integration Cost
- Worked Example: One Firm, Four Business Systems, Priced Two Ways
- The Recurring System Integration Cost After Go-Live
- Hidden Multipliers That Inflate System Integration Cost
- How to Cut System Integration Cost Without Cutting Connections
- Buy, Build or Blend: A System Integration Cost Decision Framework
- A 90-Day Plan to a Defensible System Integration Cost
- Frequently Asked Questions About System Integration Cost
- References
What System Integration Cost Covers When You Connect Business Systems
A system integration cost estimate that only covers writing code will come in at roughly a third of what you actually spend. Connecting business systems is mostly work that happens before and after the code exists.
Discovery and mapping: where system integration cost starts
Somebody has to confirm that what you want to sync is actually reachable: that the CRM exposes contact history and not just contacts, that the accounting platform accepts invoice lines through its API rather than only through its import screen, and that the two systems agree on what a “customer” is. On small projects this is days; on anything touching an ERP it is weeks. Our companion guide to ERP integration cost found that actual construction is usually a quarter to a third of first-year spend — the rest is discovery, mapping and testing.
Build, test and deployment
The visible part of the system integration cost: configuring a connector, building flows on an integration platform, or writing and hosting custom middleware. Testing is the half of this line that gets cut first and missed most — two systems that each behave correctly can still disagree about time zones, duplicates and deletions.
Monitoring, maintenance and change
Connected business systems fail quietly. An API version gets deprecated, a field gets renamed, a volume limit gets hit — and orders silently stop flowing until a customer phones. The recurring system integration cost of watching, fixing and adapting typically runs fifteen to twenty-five per cent of the build cost every year, and it belongs in the estimate from day one, not as a surprise in year two.
The Arithmetic: Why System Integration Cost Grows Faster Than Your Systems
Here is the single most useful fact in this guide: connections grow quadratically while systems grow linearly. Link every system directly to every other and the number of possible point-to-point connections is n×(n−1)÷2 — four systems have six possible connections, six systems have fifteen, eight have twenty-eight, and ten have forty-five.
The takeaway sentence before the chart: a business that doubles its systems from four to eight does not double its potential integration surface — it multiplies it by nearly five.
Why nobody builds all of them — and why the trap still bites
No sane business builds all forty-five. But the quadratic curve still drives system integration cost in two quieter ways. First, every new system you adopt arrives with an implicit question — “should this talk to the other seven?” — and even answering it costs discovery time. Second, businesses that integrate reactively, one urgent pair at a time, end up with a tangle of point-to-point links that nobody fully maps, which is precisely the estate that costs the most to maintain and the most to untangle later.
The hub alternative that caps system integration cost
The standard answer is a hub: route data through one integration layer — an integration platform, middleware, or one system elected as the master — so each system connects once to the hub rather than once to every peer. Ten systems need ten hub connections instead of forty-five direct ones. The hub itself costs money, which is exactly the trade the middle sections of this guide price out. The break-even is usually around the fourth or fifth connected system, which is why small firms rightly start point-to-point and mid-sized firms rightly stop.
System Integration Cost by System Pair
Most UK businesses do not ask “what does integration cost in the abstract” — they ask what it costs to connect this system to that one. The table below prices the most common pairs, using the project bands from our API-level guide: a simple one-way push runs £2,000–£6,000, a two-way sync with conflict rules runs £8,000–£20,000, and multi-system orchestration runs £25,000–£80,000+. Where a mainstream native connector exists, the cost drops to configuration days rather than build weeks.
| System pair | Typical pattern | Typical UK cost | Notes |
|---|---|---|---|
| Website forms → CRM | One-way push | £0–£2,000 | Native connectors and low-code tools usually cover it |
| CRM ↔ accounting | Two-way sync | £1,000–£20,000 | £1,000–£3,000 if a supported connector exists; £8,000–£20,000 custom |
| E-commerce → stock and fulfilment | Two-way sync | £4,000–£20,000 | Volume and refund handling decide the band |
| Accounting → payroll or HR | One-way push | £2,000–£6,000 | Often replaced by a monthly export if timing allows |
| Job management ↔ invoicing | Two-way sync | £8,000–£20,000 | Conflict rules on edited jobs are the hard part |
| Phone or helpdesk → CRM | One-way push | £0–£4,000 | Most modern platforms ship this as a native feature |
| ERP ↔ everything else | Orchestration | £18,000–£180,000 | £18,000–£45,000 for two or three connections; £70,000–£180,000 for four to seven |
Two siblings of this guide go deeper on the pairs that deserve their own budget line: CRM integration cost breaks down the seven drivers behind CRM-centred programmes, and the ERP guide linked above covers finance-centred ones. The system integration cost ranges above assume modern SaaS platforms with documented APIs — a legacy system without one moves you into the multipliers section further down.
Three Routes to Connect Business Systems — and What Each Really Costs
Every integration between business systems is built one of three ways. Picking the right route per connection, rather than one route for everything, is the single biggest lever on total system integration cost.
| Route | Upfront cost | Running cost | Best for | Breaks down when |
|---|---|---|---|---|
| Native connectors | £0–£3,000 setup | Often included in licences | Mainstream SaaS pairs | Your field mapping is non-standard |
| iPaaS / low-code platforms | £500–£5,000 build | £7–£120+ a month per estate | Low-volume, low-risk flows | Volume makes the per-task meter painful |
| Custom middleware | £2,000–£80,000+ per scope | £30–£200 a month hosting + maintenance | High volume, complex rules, competitive edge | Nobody documents it and the builder leaves |
Route one: native connectors
Most modern SaaS platforms ship supported connectors for their popular neighbours — CRM to accounting, e-commerce to stock, helpdesk to CRM. Where one exists and your process is standard, the system integration cost collapses to configuration: typically one to five days of somebody competent, or £0 if your team can follow documentation carefully. The catch is rigidity: connectors sync the fields the vendor chose, at the cadence the vendor chose. Confirm the connector inventory before you price anything else — it matters more than any day rate.
Route two: integration platforms (iPaaS)
Tools such as Zapier, Make and Power Automate let a capable non-developer connect business systems through a visual builder, with hundreds of pre-built app connections. They are genuinely the right answer for low-volume, low-risk flows — a form into a CRM, an order into a spreadsheet, a notification into a channel. The next section prices the main platforms in sterling, because the per-task meter is where this route’s system integration cost quietly climbs.
Route three: custom middleware
Code you own, running on cloud infrastructure you rent, doing exactly what your business needs. This is where the system integration cost bands apply: £2,000–£6,000 for a simple one-way push, £8,000–£20,000 for a two-way sync with conflict rules, £25,000–£80,000+ for multi-system orchestration. A bespoke integration also needs somewhere to run — a small container, a queue, a secrets store and monitoring, realistically £30–£200 a month on a mainstream cloud platform. Enterprise integration platforms such as MuleSoft and Boomi sit above this route, priced from roughly £25,000 to well beyond £100,000 a year; they are bought for governance and reuse across dozens of connections, not for any single one.
What the Integration Platforms Cost in Sterling
Platform pricing is published in dollars and euros, so we convert at the rates Microsoft itself uses across its own price lists: £0.752252 per US dollar and £0.856410 per euro. At the entry paid tier, the monthly prices for the four platforms UK small businesses actually shortlist come out as follows.
| Platform (entry paid tier) | List price | In sterling | Monthly allowance | Runs of a 12-step workflow |
|---|---|---|---|---|
| Make Core | $9 | £6.77 | 10,000 credits | 833.3 |
| Power Automate Premium | £11.50/user | £11.50 | 40,000 requests a day | 101,333.3 |
| Zapier Pro | $19.99 | £15.04 | 750 tasks | 62.5 |
| n8n Starter | €20 | £17.13 | 2,500 executions | 2,500 |
The last column is the honest comparison unit: how many times one twelve-step workflow can run each month at the entry tier. On that measure Power Automate Premium covers 1,621 times more volume than Zapier Pro for £3.54 a month less — a gap that per-app pricing pages are structured to hide. The chart shows the entry-tier monthly prices side by side.
The meter trap
Per-task pricing is trivial at a thousand operations a month and painful at two million: a £29 plan becomes a £900 one as volume grows, and the eventual migration to custom code costs what you thought you had saved. Model twelve months of realistic volume before committing a business-critical flow to a metered platform — the entry price is a marketing number, and the price at your real volume is the one that belongs in your system integration cost estimate. If your connected systems will push serious volume, either buy the flat-allowance platform or budget the custom build now.
The People Behind the System Integration Cost
Whoever builds your integrations, the labour is the largest line in any system integration cost. UK day rates in 2026 run roughly £450–£650 for a mid-level integration developer, £700–£950 for a specialist or solution architect, and £550–£750 blended at an agency. For the platform skills specifically, the salary index ITJobsWatch puts the median Power Platform contract day rate at £500 over the six months to 21 August 2026, on a sample of 1,647 advertised rates.
| Who builds it | Typical UK rate | Carries the risk | Watch for |
|---|---|---|---|
| Your own developer | £282.60 a day loaded cost | You | Opportunity cost of their normal work |
| UK contractor | £450–£650 a day | Mostly you | Documentation before they leave |
| Specialist / architect | £700–£950 a day | Shared | Only buy the days you need |
| UK agency, blended | £550–£750 a day | The agency | Fixed-price quotes carry a risk premium |
| Offshore team | £150–£300 a day | You, in coordination | Specification precision and review time |
The in-house arithmetic, shown in full
The £282.60 loaded day is not a guess. Take a £55,000 developer salary, add 15% employer National Insurance on earnings above the £5,000 secondary threshold and 3% pension on the full salary, and the annual cost is £64,150. Divide by 227 working days — 261 weekdays minus 8 bank holidays minus 26 days of leave — and each day costs £282.60. For context, the Office for National Statistics puts the UK median full-time salary at £39,039, so a developer building integrations is expensive time: point it at the connections that are genuinely custom, and buy the commodity ones.
Offshore honestly priced
Day rates of £150–£300 are genuinely available and sometimes work very well. Account honestly for the coordination overhead: time-zone overlap, the precision your specification now requires, and review time from somebody senior on your side. A well-run offshore build of a well-specified integration is a bargain; a vague brief sent overseas is the most expensive way to discover your own requirements.
Worked Example: One Firm, Four Business Systems, Priced Two Ways
A 25-person UK distributor runs four systems: a website taking orders, a CRM, an accounting platform, and a stock-and-fulfilment system. Of the six possible connections between them, four are actually worth having: website→CRM (new customers), website→stock (orders out the door), CRM↔accounting (quotes to invoices, both ways), and accounting↔stock (goods received to purchase ledger).
Route one: blend connectors, iPaaS and one small custom build
The CRM and the accounting platform have a supported native connector: two configuration days at the £500 median contract rate is £1,000. The two website flows are low-volume and fit an integration platform: four build days is £2,000, plus two Power Automate Premium licences at £138 a year each, £276. The accounting↔stock link has no connector and needs a small custom one-way push: £4,000, mid-band. Year-one total: £1,000 + £2,000 + £276 + £4,000 = £7,276.
Route two: build all four connections as custom middleware
Score each connection the way our API-level guide does — one point for simple, two for moderate, three for complex. Website→CRM scores 1, CRM↔accounting scores 3, accounting↔stock scores 2, website→stock scores 2: eight points. At £1,100 a point that is £8,800, plus £3,500 of fixed project costs (discovery, monitoring setup, deployment, documentation), and twenty per cent contingency on the lot: (£8,800 + £3,500) × 1.2 = £14,760, plus hosting at around £100 a month, £1,200 a year — £15,960 in year one.
What the comparison teaches about system integration cost
The blended route costs 46% of the all-custom route in year one, and the gap widens in year two: its recurring bill is £276 of licences plus roughly £800 maintenance on the one custom link, against £2,952–£3,690 maintenance plus £1,200 hosting for all-custom. But the blend is not automatically right. If the website pushed two thousand orders a day, the metered flows would be the wrong tool; if the firm competed on same-hour dispatch, owning the orchestration logic could be worth the premium. The point of pricing both routes is that the decision becomes arithmetic plus judgement, instead of whichever supplier phoned back first.
Note also what neither route includes: an enterprise integration platform. Its licence floor alone — roughly £25,000 a year — exceeds the entire all-custom build here, which is why that tier only makes sense when the system integration cost is spread across dozens of connections in a larger organisation.
The Recurring System Integration Cost After Go-Live
Every connection you build becomes a small service you run. Budget the run cost when you approve the build, because it arrives whether you budgeted it or not.
Maintenance: fifteen to twenty-five per cent a year
Vendors deprecate API versions, rename fields and change rate limits, and your own team changes processes that the mapping silently assumed. Across a portfolio of connections, maintenance runs fifteen to twenty-five per cent of the build cost a year. For businesses running several connections, a monthly retainer covering monitoring, fixes and small changes usually costs less than repeated project engagements — expect £800–£2,500 a month depending on the size of the estate. Our guide to IT outsourcing cost covers how that retainer sits alongside general support.
Monitoring is not optional
The failure mode of connected business systems is silence: the sync stops and nothing tells you. Alerting on failed runs, queue depth and record counts is hours of setup, not weeks, and it is the difference between a five-minute fix and a fortnight of quietly corrupted orders. It is included in the fixed costs of the scoring model above; if a quote does not mention it, ask why.
Licence drift
Platform allowances that comfortably covered launch volume get consumed by growth. Re-check metered plans against actual volume every quarter — the £29-to-£900 curve from the meter-trap section is a thing that happens to real businesses gradually, then suddenly. A quarterly licence review is the cheapest recurring saving in the whole system integration cost picture; the same review on the automation side cut one worked licence stack by 47% in our guide to business process automation cost.
Four things reliably turn a sensible system integration cost estimate into an embarrassing one, and none of them is the build itself.
The API paywall
A growing number of SaaS products put API access behind a higher licence tier, or meter it per call. This can dwarf the build: a plan upgrade at £30 per user per month across eighty users is £28,800 a year — several times the one-off cost of the integration that triggered it. Check the licence tier that API access requires on every system in scope before you price anything.
Data quality
Two systems can only sync records they agree about. Duplicate customers, free-text address fields and inconsistent product codes all surface the moment you connect business systems, and cleaning them is real work that the system integration cost inherits. On CRM-centred projects this is routinely the largest unplanned line — treat a data audit as part of discovery, not as an optional extra.
Legacy systems without APIs
The one system that cannot speak modern protocols sets the shape of the whole programme. The workarounds — scheduled file exports over SFTP, database-level reads, or robotic process automation driving the old interface like a human — all work, and all cost more to run than an API ever would. A desktop automation licence alone runs £115.30 a month per bot on Microsoft’s UK price list. Sometimes the honest answer is that replacing the legacy system is cheaper than integrating around it for another five years.
Security and compliance
An integration endpoint facing the internet is an attack surface, and personal data moving between systems is a UK GDPR matter — the ICO’s controller-and-processor guidance applies as soon as customer records start flowing to a third-party platform. This is a cybersecurity line in the estimate: a penetration test against an internet-facing integration endpoint costs £1,500–£5,000 and is proportionate for anything handling payments or personal data at volume. For internal-only connections, a code review against the OWASP API security risks is the lighter-weight equivalent.
How to Cut System Integration Cost Without Cutting Connections
The savings that work reduce the work, not the quality of it. Four levers, in the order to pull them.
Connect fewer things, on purpose
Revisit the arithmetic section: every pair you decline to connect is thousands saved up front and hundreds a year after. A monthly CSV export that takes somebody twenty minutes costs about £6.44 a time at a £19.31 administrator hour — automating it can wait until volume says otherwise. Rank every proposed connection by the manual minutes it removes, and build the top of the list only.
Buy the commodity, build the differentiator
CRM-to-accounting sync is the same problem in every business on earth: buy it as a connector. The logic that routes your orders your way is yours alone: that is where custom build earns its premium. Most inflated quotes put custom effort behind commodity problems.
Standardise before you integrate
Every non-standard field you insist on syncing adds mapping, testing and maintenance forever. Adopting the platform’s standard objects where you possibly can is the least glamorous saving in this guide and one of the largest — it is workflow automation working with the grain of the tools rather than against it.
Sequence the programme
Connect the pair with the clearest payback first, run it for a month, and let what breaks teach you before the next one. Big-bang integration programmes concentrate risk exactly where your team’s experience is thinnest. A sequenced programme also spreads the system integration cost across quarters, which finance teams notice and appreciate.
Buy, Build or Blend: A System Integration Cost Decision Framework
For each connection on your list, answer five questions. The pattern of answers points at the route.
| Question | Points to connectors / iPaaS | Points to custom build |
|---|---|---|
| Is the process standard across your industry? | Yes | No — it is how you compete |
| What is the realistic monthly volume? | Hundreds to low thousands | Tens of thousands and rising |
| What happens if it stops for a day? | Inconvenience | Lost revenue or compliance breach |
| Does a supported connector already exist? | Yes — use it | No, or it misses your key fields |
| Who will own it in eighteen months? | A capable admin | A developer or a retained partner |
Most 10–50 person businesses land on a blend: connectors for the commodity pairs, an integration platform for the light flows, and at most one or two custom builds where the volume or the logic demands it. That blend is what the worked example priced, and it is the shape we most often recommend. If several answers land in the custom column across many connections, you are pricing an orchestration programme — take the multi-system band seriously and read the ERP guide before anyone writes code.
A 90-Day Plan to a Defensible System Integration Cost
You can go from “no idea” to a board-ready number in ninety days without committing to a build.
Days 1–30: inventory and score
List every system, every existing connection (including the spreadsheets and re-keying that are integrations in denial), and every proposed one. Score proposed connections one to three for complexity, count the manual minutes each would remove, and check the connector inventory and API licence tier for every system. This is an afternoon of workshop and a fortnight of chasing answers.
Days 31–60: price two routes for the top three
Take the three connections with the best minutes-removed-per-point ratio and price each two ways, exactly as the worked example does — blended route and custom route, with the licence maths at your real volumes. Get one external quote per route; the spread between quotes is itself information about how well you have specified the work. Our guide to Power Automate consulting cost covers what platform-specialist help costs at this stage.
Days 61–90: pilot one connection end to end
Build the single best-ratio connection, instrument it, and run it for a month. Measure the minutes actually saved against the estimate, log every failure and its cause, and only then approve the programme. A £2,000 pilot that exposes your data quality problem is the cheapest £2,000 in the whole system integration cost budget.
Frequently Asked Questions About System Integration Cost
How much does it cost to connect two business systems in the UK?
The system integration cost for one straightforward, one-directional connection between two modern SaaS platforms is £2,000–£6,000, delivered in two to four weeks — and £0–£3,000 if a supported native connector covers it. Bidirectional sync with conflict rules runs £8,000–£20,000. Anything orchestrating three or more systems starts at £25,000.
What does ongoing maintenance cost?
Fifteen to twenty-five per cent of the build cost a year, or a retainer of £800–£2,500 a month across a small estate. That covers deprecations, schema changes, monitoring and small enhancements. Budgeting nothing for maintenance is the most common defect in system integration cost planning — the second most common is forgetting the licence meter.
Is an integration platform cheaper than custom code?
At low volume, dramatically — the system integration cost at entry tiers runs £6.77–£17.13 a month, against thousands for a build. At high volume the meter reverses the answer: model twelve months of your real volume on each platform’s pricing before deciding, and remember the flat-allowance platforms cover orders of magnitude more runs for similar money.
Can we do it in-house?
If you have a developer, yes for custom builds at £282.60 a loaded day; if you have a careful administrator, yes for connectors and platform flows. The honest constraints are opportunity cost and continuity — who maintains it when the builder moves on. Write documentation into the definition of done, whoever builds it.
How long does connecting our systems take?
A native connector: days. An integration platform flow: days to two weeks. A custom two-way sync: four to eight weeks including testing. A multi-system programme: a quarter to a year. The calendar is usually gated by access, sign-off and data cleaning rather than by the build itself.