Ask ten software companies what a custom ERP costs and you will get ten different answers, most of them a version of "it depends". That answer is annoying, but it is honest. The useful question is what it depends on, because once you know the factors you can control most of them.
This post does not give a price. We quote every custom project per requirement, and a number printed in a blog post would be a guess that does not match your business. What follows is the list of things that move the cost, how to scope a project so the quote is meaningful, and how to tell whether you need a custom build at all.
We build custom ERP systems, and we also make IDP, a ready-made system for inventory, sales and accounts. So we have a stake on both sides of this decision. We will try to be straight about which one suits which business.
What a custom ERP actually is
An ERP is one system where the parts of a business share the same data: stock, sales, purchasing, customers, suppliers and accounts. When a sale is entered, stock falls and the ledger updates without anyone typing it a second time.
"Custom" means it is built around how your business works, rather than you adapting to how a product was designed. That can mean a whole new system, or a few specific modules added next to something you already use.
The factors that decide the cost
These are the same factors we ask about in a first conversation. Roughly in order of how much they matter:
- Scope. The number of distinct things the system has to do is the biggest driver. A system that handles stock and invoicing is a different size of project from one that also covers production, approvals, field staff and reporting for several departments.
- Modules. Each module (inventory, sales, purchasing, accounts, assets, and so on) has its own screens, rules and reports. Ten modules is not ten times one module, because they also have to talk to each other, but the work does grow with the count.
- How unusual your rules are. Standard processes are cheaper than unusual ones. If your pricing, approvals or stock rules work differently from the common pattern, that logic has to be designed, built and tested from scratch.
- Integrations. Connecting to a payment provider, an accounting package, a courier, a website or a government portal means working to someone else's rules. Each one adds build and testing time, and some break when the other side changes.
- Data migration. Moving years of records out of spreadsheets or an old system is often underestimated. Messy product lists, duplicate customers and inconsistent naming have to be cleaned before they go in, and someone has to check the result.
- Users, roles and locations. More users usually means more roles and permissions to design. Multiple branches or warehouses add rules about who can see and change what, and where stock sits.
- Offline needs. If staff must keep working when the internet drops, the system has to store data locally and reconcile it later. That is real engineering, and it is a different design from a browser-only system.
- Reporting. A handful of standard reports is one thing. Custom dashboards and exports for management, auditors or tax filing are another.
- Support and change after launch. Software is not finished at go-live. Training, bug fixes, hosting, backups and new requests all have a cost, either inside the project or as an ongoing arrangement.
Why the same words mean different prices
Two businesses can both ask for "an ERP with inventory and accounts" and need very different things. One has a single shop, a standard invoice and clean data. The other has three warehouses, credit terms per customer, a legacy system to migrate and staff who work offline. The label is the same. The work is not.
That is why a quote built from a short description is a weak number. A quote built from a written scope is a much better one.
How to scope a project so the quote means something
You do not need technical language. You need clear answers to a few questions, written down:
- What problem are you solving? Name the two or three things that go wrong today: stock that does not match, invoices typed twice, no view of what customers owe.
- Who uses it? List the roles (cashier, storekeeper, accountant, owner) and what each must be able to do and must not be able to do.
- Where does the data live now? Spreadsheets, an old program, paper? How much of it needs to come across?
- What must it connect to? List every outside system, even small ones.
- How many locations, and can they lose internet?
- What can wait? Separate the must-haves for day one from the nice-to-haves. This is the cheapest lever you have.
Handing a vendor a one-page version of those answers will get you a more accurate and more comparable quote than any feature checklist.
Phasing: the way to control a budget
Building everything at once is rarely necessary. A common approach is to start with the module that hurts most, often stock and sales, get it into real use, and add the rest once the first part is proven. You spend less before you have learned anything, and you find out early whether the design suits how your staff work.
Phasing also lets you change your mind. Requirements you wrote on day one will not all survive contact with real use, and it is cheaper to discover that after phase one than after the whole build.
Build or buy: when a custom ERP is worth the cost
In the UK, people tend to search for a "bespoke ERP system" and mean the same thing as "custom ERP" elsewhere. Whichever word you use, the decision is the same: build to fit, or adopt something that already exists.
A ready-made product is usually the better choice when:
- Your processes are fairly standard for your type of business.
- You want to be working in days or weeks, not months.
- You would rather pay a published monthly price than fund a build.
- Your needs are mainly inventory, sales, customers, suppliers and accounts.
A custom build starts to make sense when:
- Your workflow is genuinely different and is part of how you compete.
- You need to connect several systems that no product connects out of the box.
- You have already tried a ready-made product and are working around it every day.
- You need specific roles, approvals or reports that no product offers.
IDP covers inventory across multiple warehouses, sales and invoicing, customers and vendors with balances and credit limits, a cashbook, profit and loss, a balance sheet, fixed-asset depreciation, and roles and permissions. It runs offline-first on Windows, macOS and Linux, with a cloud-hosted option. Payroll and manufacturing are not among its listed modules. If your needs sit inside that list, IDP is likely enough and will cost you less than a build. If they do not, a custom system is the honest answer.
Questions to put to any ERP vendor
- What exactly is in the scope, and what is not?
- How do you handle changes once the work has started?
- Who owns the code, and will I get access to it? (Ask for this in writing before you sign. Whatever a vendor says, the contract should say it too.)
- How is my data migrated, and who checks it?
- What does support look like after launch, and what does it cost?
- Can I see a working version early, before everything is finished?
Our guide to evaluating business software before you commit covers how to test a product on your own data, and the same habit applies to a custom build: ask to see real progress on real cases, not slides.
Where to start
Write the six scoping answers above, even roughly. If you are still running on spreadsheets, our post on why growing teams outgrow Excel can help you decide whether the pain is big enough to justify a system at all.
When you are ready, see how we approach custom ERP development and talk to us. Tell us what you have and what goes wrong, and we will quote it per requirement and explain what is driving each part of the quote.
FAQ
How much does a custom ERP cost?
There is no single answer, and we do not publish figures, because the cost depends on your scope, modules, integrations, data migration, users, locations and support needs. We quote each project per requirement after understanding what you need.
Why do custom ERP quotes vary so much between vendors?
Often because the vendors are pricing different scopes. One may assume clean data and no integrations, another may include migration, training and support. Give every vendor the same written scope and compare like for like.
Does a bespoke ERP cost more than off-the-shelf software?
Usually, at the start. A ready-made product has a published monthly price, while a bespoke ERP (the UK term for a custom ERP) is a build quoted for your business alone, so the same cost factors apply. It can still be the better value if you are working around a ready-made product every day, or paying for several tools that one system would replace.
Can I start small and add modules later?
Yes, and it is usually the sensible way to control budget and risk. Start with the area that causes the most trouble, use it for real, then extend. Plan the data structure up front so later modules connect cleanly.
When does a ready-made system like IDP cost less than a custom build?
When your needs are inventory, sales, customers, suppliers and accounts, IDP is likely enough and will cost you less than a build. If you need unusual workflows, specific integrations or features outside its listed modules, such as payroll or manufacturing, a custom build is the better fit. See the product page for the full module list.