MedusaJS B2B e-commerce guide 2026

Medusa v2 is a commerce layer, not an ERP replacement. The platform gives you pricing, customer, cart, order and workflow modules that you use to build per-customer price lists, customer groups, B2B cart, custom checkout and integrations. MOQ, credit limits and order approval are usually domain logic in the implementation, not checkboxes without discovery.

Typical B2B needs two data layers: Medusa holds catalog, cart, checkout and commercial rules required by sales channels; ERP (SAP, Comarch, Microsoft Dynamics, custom WMS) stays the source of truth for invoices, stock and credit limits. GMI designs event-driven sync to avoid price drift across channels.

The B2B storefront is usually Next.js with company login, per-account price views, multi-line carts and order history. The same Medusa Admin API can power a React Native app for field sales.

Many guides show catalog, cart and checkout. That is a useful start, but real B2B starts where D2C ends: multiple buyer roles, department budgets, credit limits, contract price lists, invoices, split deliveries, partial fulfilment and manual sales-team decisions.

The biggest risk is not the Next.js storefront itself. It is who can change price, which system approves credit, how fast ERP returns stock and what happens to an order when one vendor or warehouse cannot confirm availability.

That is why GMI treats Medusa B2B as operating architecture, not a “launch a store” project. In discovery we split decisions into three layers: buyer experience, commerce logic in Medusa and source of truth in ERP/PIM/WMS.

Contract pricing: price lists tied to customer groups or individual B2B accounts, often with validity dates and per-market currency. Credit limits: block checkout when balance is exceeded or require prepayment for new accounts.

Approval workflows: a manager approves orders above a threshold before they hit ERP. Reorder and quick order: last-SKU lists per customer shorten purchase cycles in wholesale and distribution.

Integrations: product sync from PIM, stock from warehouse, shipment confirmations from WMS, pro forma invoices from ERP. In discovery we map which events are real-time versus nightly batch - that drives cost and SLA.

GMI ranges for Medusa B2B with ERP and migration: EUR 55,000 - 120,000 fixed price after DDT (1-3 week discovery). MVP checkout + contract pricing: 3-5 months. Full programme with migration and multiple integrations: 5-9 months.

Reference team: Medusa tech lead, 2 backend devs, Next.js frontend, QA and client-side product owner. 2-week sprints with demos, internal code review, architecture docs in English.

Post go-live we recommend a maintenance retainer (Medusa updates, monitoring, peak-season B2B support). Broader headless commerce context lives on our headless e-commerce page.

The first mistake is copying the monolith 1:1. If Magento or ERP has ten years of commercial exceptions, not every exception belongs in the MVP. Some rules must be named, some removed and some left in ERP as a manual phase-two process.

The second mistake is “real-time everything”. Prices and checkout availability often need fresh data, but invoices, reports and parts of order history can run in batch. A good B2B architecture separates cart-critical data from reporting data.

The third mistake is no post-go-live plan. Medusa is open source and flexible, but it still needs maintenance: updates, monitoring, regression tests, peak support, integration checks and a business-change roadmap.