What a custom ERP is, in plain terms
ERP stands for enterprise resource planning, which tells you almost nothing. In practice, an ERP is the system where a company's operational data lives together: orders, jobs, projects, stock, purchasing, people, time, invoicing and the reports built on top of them.
A custom ERP is that system built for one company. Instead of adopting a big platform's idea of how a business should run and paying consultants to adapt it, you build the modules you need, with your rules, your roles and your vocabulary.
For a company with 20 to 300 people, 'ERP' rarely means the full enterprise suite. It means one place where sales hands work to operations, operations hands it to finance, and the owner can see what's happening without asking five people.
Why ERP projects fail
Before deciding how to build, it helps to know how these projects usually go wrong. Most failures come from the same few causes, and none of them are about technology.
- Starting with everything: trying to replace every process in one go, so nothing goes live for a year and the business has changed by then.
- Copying the old mess: moving broken processes into new software instead of asking why each step exists.
- Forcing the company into a template: adopting a platform's standard process and discovering later that the non-standard parts were why customers chose you.
- No owner on the client side: the project belongs to IT or to a consultant, not to the people who run the operation.
- Data migration left to the end: discovering in the last month that ten years of data doesn't fit the new structure.
- Hourly billing with no fixed scope: every unclear requirement becomes more hours, and the budget drifts with it.
Off-the-shelf ERP vs custom ERP: a comparison
Both are valid. Here is how they compare for a mid-sized company.
- Process fit. Off-the-shelf: good for standard processes like accounting and simple distribution. Custom: exact, including the steps that make you different.
- Implementation. Off-the-shelf: configuration, customisation and consultant time, often longer than expected. Custom: build time, but scoped to what you use.
- Licensing. Off-the-shelf: per user or per module, rising as you grow. Custom: no licences; you pay for hosting and support.
- Change. Off-the-shelf: you wait for the vendor or pay for customisation that may break on upgrade. Custom: you change it when the business changes.
- Accounting and compliance. Off-the-shelf: often strong, with local tax rules built in. Custom: best left to your existing accounting software, connected by integration.
- Risk. Off-the-shelf: vendor dependence and upgrade projects. Custom: builder dependence, reduced by owning code, data and documentation.
Keep accounting where it is
The most useful rule in custom ERP development: don't rebuild your accounting. Accounting packages handle local tax rules, statutory reports and audit requirements that change every year. Your accountant knows them. There's no advantage in rebuilding that.
Instead, the custom ERP handles everything operational and sends clean, structured data into accounting: invoices, payments, costs by job or project. It reads back what it needs, like payment status. That integration is a well-understood small project, and it removes the copy-paste between operations and finance that eats hours every week.
The same logic applies to payroll. The ERP prepares clean hours, shifts, absences and bonuses. Payroll software or your payroll provider does the statutory calculation.
Modules to consider, and which to build first
A custom ERP is built in modules around one shared database. The order matters more than the list. Start where the most re-typing and the most mistakes happen, usually at the hand-off between selling and doing.
- Orders, jobs or projects: the unit of work your company delivers, with status, owner, dates and costs.
- Clients and sales: the CRM part, connected directly to the work it produces.
- Scheduling and resources: people, vehicles, equipment and sites, with conflicts visible.
- Stock and purchasing: what you have, where it is, what's reserved, what needs ordering.
- Time and attendance: hours per person per job, feeding both payroll prep and job costing.
- Invoicing and payments: invoices generated from the work done, sent to accounting, chased when overdue.
- Documents and approvals: contracts, reports, photos, sign-offs attached to the right record.
- Owner dashboard: margins by job, cash expected, work in progress, overdue items.
How to phase a custom ERP
The safest way to build an ERP is to make the first phase small enough to go live in weeks, and useful enough that people want the second phase.
Phase one typically covers the core unit of work and the hand-offs around it: a job or order is created, scheduled, done and invoiced, with the data migrated from spreadsheets. That alone often removes most of the daily chaos.
Phase two adds depth: stock, purchasing, time tracking, integrations with accounting and banking, a client portal. Phase three adds intelligence: automations that chase invoices and fill gaps, and an AI layer that answers questions and plans work.
Each phase has a fixed price and a go-live date. You can stop after any phase and still have a working system. That's the opposite of the classic ERP project, where nothing works until everything works.
A practical way to choose phase one: list every hand-off in the company and mark the ones where work gets lost, delayed or re-typed. The cluster with the most marks is your first phase. It's rarely the module people name first in a meeting, and it's almost always where the owner's daily frustration comes from.
Integrations that usually matter
Most companies keep some tools, and they should. The ERP becomes the centre, and the rest connects to it.
Common integrations are accounting, banking for payment matching, email and calendars, e-commerce or ordering platforms, supplier catalogues, telephony and industry-specific portals. Each is a small, bounded project. With us, Maxxed includes up to four integrations and each extra one is €4,500.
A useful test for each connection: which person stops re-typing what, and how often? If the answer is nobody or rarely, skip it for now.
Data migration: the part that decides go-live
In most ERP projects, the software is not the hard part. The data is. Years of spreadsheets, exports from old tools, half-filled fields, duplicate clients spelled three ways and stock counts nobody fully trusts.
A sensible migration happens early, not in the last week. The builder maps each old source to the new structure, runs a first import on a sample, and shows the people who know the data what came out. They spot the problems in minutes that a developer would never notice: a client that merged with another, a price list that stopped being valid, a product code reused for something else.
Then the full import runs, gets checked again, and the old files become read-only. That last step matters. If the spreadsheet stays editable, half the team will keep using it, and you'll have two versions of the truth. We include full data migration in every plan because a system with empty or wrong data dies in month two.
Roles, permissions and the people who use it
An ERP touches almost everyone in the company, and each group needs something different. If everyone gets the same screens, the system feels heavy to all of them.
Office staff need speed: keyboard-friendly lists, bulk actions, clear queues of what needs doing. Field staff need a phone view that works offline, shows today's work, and lets them log time, photos and signatures in seconds. Managers need their team's workload and exceptions. Finance needs clean, approved data. The owner needs a dashboard and the ability to ask a question.
Permissions follow the same logic. A branch manager sees their branch. A technician sees their jobs. A client, through a portal, sees their own orders and invoices. Designing this properly is a large part of the work, and it's one of the main reasons custom beats configured: the permission model follows your organisation chart instead of a vendor's.
Security from the first day
An ERP holds the most sensitive data a company has: prices, margins, salaries, client details. Security can't be a later phase.
The basics to insist on: individual accounts with strong authentication, role-based access, an audit log of who changed what, encrypted backups tested by actually restoring them, monitoring with alerts, and a clear plan for what happens when someone leaves the company. For groups of companies, add a security review and access controls per entity. We also offer security audits, hardening and 24/7 monitoring as a separate service if your wider IT needs it.
Where AI fits in an ERP
An ERP is full of structured data, which is exactly what makes an AI layer useful rather than decorative. When the AI sits on top of your real records and respects each user's permissions, people can ask in plain language and get answers from the actual numbers.
Examples: 'what are we running out of next week', 'which jobs are over budget', 'who hasn't paid us this month', 'plan next week's shifts around these absences'. Beyond answering, AI staff can do work: a clerk that prepares invoices from completed jobs and chases late payments, a receptionist that books work into the schedule, a caller that confirms appointments.
The AI should be the last layer, not the first. It's only as good as the data model beneath it.
What it costs
Custom ERP costs are driven by roles, hand-offs, integrations, data migration and whether you add the AI layer. Company size matters less than process complexity.
Our pricing is public and fixed before we start. Core is €18,000 for one company on one system with up to five roles, data migration, phone and desktop access, an owner dashboard and three months of support, typically live in three to four weeks. Maxxed is €48,000 and adds unlimited roles, the AI layer, up to four integrations, automations, a client portal and six months of support, typically live in six to eight weeks. Empire starts at €120k for groups of companies across several countries, with consolidated reporting across entities and currencies, a dedicated team and twelve months of support.
After the support period, Maxxing Care is €2,900 per month for changes, new features and priority fixes. Hosting is a separate, modest line; ask any builder where the system runs and in whose account.
How to pick a custom ERP builder
You're choosing a partner who will understand your operation better than most of your staff. Choose accordingly.
- They start by looking at how work really moves, not by sending a requirements questionnaire.
- They give a fixed price per phase, and explain exactly what counts as a change.
- They show working software on your data early, not slides.
- They recommend keeping accounting and payroll in specialised tools.
- You own the code, the data and the documentation.
- They have a clear answer on security: access control, backups, audit logs and monitoring.
- They say no to things that won't pay back.
Getting started
Before talking to any builder, list your units of work, every hand-off between roles, the tools and spreadsheets involved, and the five questions you'd like the system to answer every morning. That's the skeleton of a good first phase.
If you'd like to do this with us, apply and show us how the company runs today. We reverse-engineer it, give you a fixed quote, and after kickoff you get a first working version on your own data within 24 hours.