The Essential ERP Modules for an SMB

An overview of the essential ERP modules

A custom ERP is not a monolithic block: it is an assembly of business modules that share a single database and a single access-control logic. That is precisely where the value lies. Rather than enduring the hundreds of functions of a generic software package of which you will use only a fraction, you compose the perimeter your business actually needs. Before prioritizing, you need to know the map. Here are the six module families that come up in nearly every SMB project, each addressing a specific business flow.

1. Invoicing and sales management. The financial core of the ERP: quotes, purchase orders, invoices, credit notes and reminders from a single source. A validated quote automatically feeds the invoice, with no re-entry or copy error. Payment collection is integrated through Stripe, which closes the loop between the sale and the payment. It is the module most often deployed first, because it makes cash flow reliable from go-live.
2. CRM and sales. Centralizing contacts, opportunities and the history of the client relationship. Sales reps track their pipeline, the manager sees the conversion rate, and every quote issued from the CRM connects to the sales module without a break. A CRM aligned with the business avoids the pitfall of generic tools that impose their vocabulary instead of fitting yours.
3. Purchasing and inventory. Tracking suppliers, replenishment orders and real-time stock levels. For a business that handles products or consumables, this module avoids both stockouts and overstocking. It links to the sales module to decrement stock at each sale and trigger reorders at the right threshold.
4. HR and payroll. Managing staff, leave, time and the variable payroll elements. Payroll itself is often still handled by an expert-comptable (chartered accountant), but the ERP prepares and consolidates the data upstream. This module also structures the access rights: who validates what, who sees which sensitive information.
5. Project management. Task planning, time tracking, milestones and profitability per project. Indispensable for service and consulting activities, where margin is decided by tracking hours. Logged time feeds invoicing directly, which turns a timesheet into traceable revenue.
6. Reporting and steering. Consolidated dashboards that aggregate the data from every other module: revenue, margin, outstanding balances, team workload. This is the layer that turns the ERP from a data-entry tool into a decision tool. Without reporting, you record the data without ever reading it.

These six families do not simply add up mechanically. They reinforce each other: a CRM without invoicing loses half its value, inventory without sales management runs empty. It is this interconnection that separates an ERP from a collection of juxtaposed tools. And it is also why the deployment order matters as much as the list itself. In practice, an SMB activates only 2 or 3 of these 6 families at launch, with sales management and its Stripe payment collection almost always leading the way.

How to prioritize modules: the MVP logic

The temptation, faced with this map, is to want everything at once. That is the costliest mistake. An ERP that tries to cover the six families from day one multiplies the budget, stretches the timeline and delays the moment the tool becomes useful. The method we apply is the MVP, the minimum viable product: we identify the two or three modules that deliver the most value immediately, we ship them fast, then we enrich the perimeter at the company's real pace. This approach spreads the investment and turns the ERP into a tool that grows with you rather than a project that overwhelms you.

To prioritize, three questions are enough. Which flow makes you lose the most time today? Which flow generates the most costly errors? Which flow directly conditions your cash flow? In the vast majority of SMBs, these three answers point to sales management and invoicing. That is why this module almost always opens the ball: it saves time from the very first week and makes payment collection reliable. The CRM or project tracking often follow in a second wave, once the sales base is solid.

Concretely, a first structuring scope rarely holds more than three modules. For a resort in Thailand that we supported, the challenge was not to stack standard functions but to centralize operations scattered across disparate tools and spreadsheets. The initial perimeter was therefore built around the field teams' real flows, not around a theoretical catalogue of modules. This discipline of the minimum perimeter is what separates an ERP that is delivered and adopted from a project that bogs down. We prefer two excellent, used modules over six average, neglected ones.

Our modular approach, step by step

Composing an ERP by modules is not an isolated technical act: it is a method that starts from the business and works down to the code. Here is the sequence we follow to scope a perimeter, from diagnosing the flows to adding new modules once the foundation is adopted. Each step locks in the next, which avoids developing a module nobody really needed.

This modular approach is also what makes the investment legible. You know what each module covers, why it is there, and what it costs. Nothing is billed to pad the count. And since everything rests on the same technical base, adding a module 6 months later does not mean rebuilding everything: the foundation, the access rights and the data are already in place. It is exactly the sequence followed on the ERP of a resort: a foundation of 2 to 3 modules scoped first around the field flows, secured by Supabase RLS, then enriched as usage grows.

Cost per module: how the budget is built

The question of price comes up fast, and the honest answer is that there is no fixed per-module rate, because two invoicing modules can cover very different realities. What sets the budget is the number of modules, their functional complexity, the volume of integrations with your existing tools and the number of users. A first structuring business scope sits between EUR 30,000 and 90,000, within an overall ERP range of EUR 15,000 to 150,000. The low end corresponds to a target foundation of two or three modules, the high end to a full business system, multi-module and multi-integration.

To make this range concrete, here is how the effort breaks down by module. A sales management module, almost always in the initial foundation, concentrates a large share of the first perimeter because it touches the financial core and the Stripe integration. Modules that connect to many others, such as reporting, cost less in development of their own but depend on the quality of the modules they aggregate. Business-specific modules, the ones no market software offers, are those that genuinely justify going custom and weigh the most in the budget.

The MVP logic protects this budget. Rather than committing EUR 150,000 to a theoretical perimeter, you focus EUR 30,000 to 90,000 on the foundation that delivers value immediately, then decide what comes next based on real usage. Investment follows value, not the other way round. That is exactly what we price during the diagnosis: a realistic first perimeter, module by module, with no useless surface.

Example: the modular foundation of a resort

A concrete case illustrates this modular logic better than a catalogue. A resort in Thailand that we equipped was running its operations across a mosaic of disparate tools and spreadsheets. The flow of information between the field teams and administration stayed slow and error-prone. The challenge was not to tick the six module families, but to identify the flows that genuinely wasted time and centralize them in a single interface. The perimeter was therefore structured around the resort's daily operations, and integrated with the existing system rather than replacing everything at once.

The lesson holds for any SMB: the right question is not how many modules an ERP should contain, but which modules genuinely save time and make the business reliable. You start from the flows, scope a foundation of two to three modules between EUR 30,000 and 90,000, secure the access rights with Supabase RLS, then enrich at the pace of needs. That is precisely what our free diagnosis helps to lay out: a map of your flows, a prioritized list of modules and a priced first perimeter, with no commitment and a reply within 24 hours.