ERP Integration for SMBs: Connect Your Business Software

The integration challenge: application silos and duplicate entry

Before talking about ERP, look at the actual daily routine of an SMB. A sales rep enters a client in the CRM, the bookkeeper re-enters them in the invoicing software, an assistant copies the delivery address into the shipping tool, and the owner tries to consolidate it all in a spreadsheet on Friday evening. Every tool works, but none of them talks to the others. This is what an application silo is: an isolated island of data whose information never flows automatically to the other systems. An SMB frequently accumulates three to five tools that each hold a partial version of the same client record.

The direct consequence has a name: duplicate data entry. The same information is typed two, three, sometimes five times, by different people, at different moments. At best, it is wasted time. At worst, it is a source of errors that propagate: a wrong address produces a failed delivery, a mistyped amount skews the invoicing, a forgotten date triggers a reminder at the wrong moment. The larger the company grows, the more these frictions multiply, because the number of tools grows faster than the capacity to coordinate them by hand. Silos never show up on a balance sheet, but they are paid for every day in wasted hours and unhappy customers.

A custom ERP exists precisely to break these silos. Rather than stacking one more tool, it becomes the point of reference where data is entered once, then distributed to every department that needs it. But that promise only holds if the ERP is properly integrated with the existing ecosystem. A central system that does not connect to accounting or to the payment solution just recreates a silo, a bigger one. Integration is therefore not a technical option for the end of the project: it is the core of what an ERP is worth. On one of our ERP projects for a resort in Thailand, operations were run through a mosaic of tools and spreadsheets before being centralized on a single platform.

The key integrations of an SMB ERP

Not every ERP needs to connect to the same systems, but five integration families come up in nearly every SMB project. Mapping them upfront avoids discovering a critical need mid-project. Here are the connections we set up most often, with their precise role in the chain.

1. Accounting. The ERP must feed the accounting software without re-entry: sales entries, invoices, payments and credit notes. Synchronization can run through an API when the accounting tool exposes one, or through a structured export in the format your accountant expects. The goal is that an invoice validated in the ERP lands in the books without a single line copied by hand, and that bank reconciliation stays reliable.
2. Payments with Stripe. To collect payments online, manage subscriptions or trigger direct debits, Stripe is our reference building block. The ERP creates a payment intent, Stripe processes the transaction, then a webhook returns the status to the ERP, which updates the order and the invoice in real time. This event loop guarantees that a successful or failed payment is reflected in the system immediately, with no manual checking. Dunning for failed payments becomes automatic too.
3. Transactional email with Brevo or Resend. Order confirmations, due-date reminders, internal notifications and follow-ups go out through Resend for transactional email and Brevo for more marketing-oriented campaigns. The ERP triggers the send at the right moment, with the right data, and logs what went out. No more forgotten or duplicate reminders: the business event (an unpaid invoice, a shipped order) directly drives the communication.
4. E-commerce. When the company sells online, the ERP synchronizes with the store: catalog and stock in one direction, orders in the other. A sale on the site decrements stock in the ERP, which becomes the source of truth, and a stockout recorded on the ERP side is reflected in the store. This two-way synchronization eliminates phantom overstock and sales of unavailable products, two classic wounds of multichannel commerce.
5. Business APIs. Every sector has its specific tools: shipping software, an e-signature platform, a geolocation service, a supplier or marketplace API. A custom ERP consumes these APIs to pull in or push out data as needed. That is the flexibility of bespoke development: you integrate exactly the services the business needs, without paying for useless generic connectors.

These integrations rest on our real stack: Next.js and strict TypeScript for the code, Supabase for the database and authentication, Stripe for payments, Resend and Brevo for email, all deployed on Vercel. On this type of project, it is the real workflows of field teams that dictate the integrations, not the other way around: we connect what serves the business, not what looks good on a diagram.

Our API-first approach to durable integrations

How you integrate matters as much as what you integrate. An integration cobbled together at the end of a project, with one-off scripts and manual synchronization, becomes debt that breaks at the first change. Our choice is the opposite: an API-first approach, where every ERP module exposes its data through a documented API from the moment it is designed, and consumes data from other systems the same way. Concretely, integration is not a patch added after the fact: it is a native property of the architecture. That makes connections more robust, more testable and reversible: you can swap a third-party tool without rebuilding everything.

This method relies on two complementary mechanisms. APIs, first, to query or update data on demand, for example fetching a client balance or pushing an order. Webhooks, second, to react to an event without polling in a loop: Stripe tells the ERP a payment went through, the ERP tells Brevo an invoice is overdue. This event-driven model avoids heavy synchronization jobs and delivers flows in near real time. Here is the sequence we apply on every integration project.

This rigor has a cost, built into the range of a custom ERP: from 15,000 to 150,000 EUR depending on the number of modules, integrations and users. But it is a cost that pays itself back: every solid integration removes recurring hours of re-entry and errors that never appear on any quote.

Flow security and reliability: GDPR and Supabase RLS

Integrating systems means moving data around, often personal data: names, addresses, amounts, purchase histories. Security is therefore not an add-on, it is a precondition. Our foundation rests on Supabase and its RLS (Row Level Security) policies, which enforce isolation directly at the database level. Concretely, every row carries its own access rules: a user can only read or modify the data they are entitled to, and in a multi-tenant context, one client's data stays strictly partitioned from another's. This isolation does not depend on the application code behaving well: it is enforced by the database, which makes it a far stronger guarantee than a simple server-side filter.

GDPR compliance revolves around 3 principles we apply by default. Minimization, first: only the data strictly necessary for each integration is transmitted, never the whole client file. Encryption, next, in transit over HTTPS and at rest on the database side. Traceability, finally: flows are logged, which makes it possible to know which data went where, and to answer an access or deletion request. The stakes are not theoretical: the GDPR (Article 83) provides for penalties of up to EUR 20 million or 4% of worldwide annual revenue, whichever is higher. Hosting on Vercel and Supabase lets us favor European regions, a recurring concern for SMBs that care about where their data lives.

Reliability completes security. A flow can fail for a thousand reasons: a third-party service under maintenance, a network outage, a slow response. Our answer rests on 3 mechanisms. Webhook signature verification guarantees an event really comes from Stripe or the expected system, not from a malicious actor. Automatic replays retry a failed flow rather than abandoning it. And logging makes every exchange auditable, which turns an incident into usable information rather than a mystery. A payment must never be collected without the order being updated, nor a reminder sent twice: these idempotency guarantees are built in from the design stage.

Example: a resort with its operations finally centralized

Integration makes the most sense on a concrete case. A resort in Thailand we equipped was coordinating its operations across a mosaic of disparate tools and spreadsheets. Data moved slowly between field teams and administration, and every information handoff was an opportunity for error or delay. It is the textbook profile of an organization held back by its silos: each tool was useful locally, but the lack of connections between them forced re-entry and deprived management of a consolidated view of the business.

The answer was to design a custom ERP centralizing operations management in a single interface, with modules structured around the teams' real workflows and integrated with the existing system. Rather than brutally replacing every tool, the ERP became the point of reference where data is entered once and then shared. Operations are now run from a single platform, with information flowing more smoothly between departments and a consolidated view of the resort's activity. That is exactly what integration designed from the start makes possible: not one more tool, but a system that finally gets the others talking to each other.

The approach is the same for any SMB: we do not bolt integrations onto closed software, we design them into the foundation: API-first, with RLS security and flow reliability as baseline requirements. Data entered once, tools that talk to each other, teams that stop copying: that is the kind of time reserve our free assessment identifies and prioritizes, with no commitment and a reply within 24 hours.