There's an invisible job that eats hours in almost every company running an online store: re-typing. Orders from the site into the ERP, stock from the ERP to the site, prices updated "as soon as possible". Every copy is lost time and a lurking error — and the customer who orders an out-of-stock product will gladly confirm it.
The three flows to put in order
Catalog and stock (ERP → site). The warehouse is the source of truth: products, variants, prices and availability must flow to the site by themselves. The key is incremental sync: only what changed gets updated — so even a catalog of tens of thousands of SKUs stays aligned in minutes, not overnight imports.
Orders (site → ERP → courier). An online order should be born inside the ERP: customer record, lines, reserved stock, shipping document. When this flow is automatic, fulfilment starts in minutes and nobody re-types addresses.
Payments and reconciliation. Gateway payouts, fees, refunds — automatically matched to orders, so accounting reconciliation stops being one afternoon per month.
"But my ERP is old and closed"
The most frequent objection — and almost never a blocker. If there are no APIs, you find the available door: scheduled exports, direct database access, exchange files. I've synced catalogs of 90,000+ SKUs starting from exports of an ERP for which "closed" would be a compliment. The e-commerce platform — Shopify, WooCommerce or custom — always has APIs anyway.
Where to start
With the flow that bleeds the most. Usually it's stock (selling what's out of stock) or orders (hours of manual re-entry). Integrate that one, measure, move to the next.
The full track is described in E-commerce integrations. Want to know which flow to start with in your case? Let's talk — the flow analysis is the fast part.