Until the store and the stock system talk to each other, somebody in the company is a human cable - retyping stock, prices and orders, with errors included. In Polish trading companies the heart of operations is usually an ERP or trade-and-stock system: Subiekt (GT/nexo), Comarch Optima, enova365, WF-Mag, Symfonia. An online store adds a second world - and those two worlds have to be joined so that there is only one truth.
Rule number one: decide who is the source of truth
Before the word “plugin” is spoken, settle the directions of flow:
- Stock levels: ERP to store. The warehouse knows better; the store only displays. A sale in the store comes off stock in the ERP through the order, not through a manual correction
- Prices: ERP to store (usually). Price lists, including per-customer wholesale ones, live in the ERP; the store shows them. The exception: purely online promotions
- Products: most often ERP to store, with content filled in on the store side (descriptions, photos, SEO - the ERP cannot do that)
- Orders: store to ERP. An order from the store creates a document in the ERP and reserves the goods; the invoice follows from there - which under the KSeF obligation has stopped being cosmetic
Many failed integrations die not on the technology but on the absence of those decisions: two systems edit the same field and overwrite each other.
Integration routes
- An off-the-shelf connector - for popular pairings (Subiekt to WooCommerce, Optima to WooCommerce) there are maintained integrators. The cost: a licence or subscription plus the rollout; they cover the standard flows and are the fastest route
- Through a sales integrator (Baselinker, for example) - when marketplaces are also in play; the ERP feeds stock, the integrator distributes it across channels and collects orders. I describe that setup at more length in the piece on Baselinker
- A bespoke integration - written for your process when the standard does not cover the logic (unusual reservations, production, multiple warehouses, B2B with credit limits). The most expensive and the most precisely fitted; the budget depends on the number of flows and the complexity of the logic
An old ERP version with no API can be the biggest cost in the project - sometimes it is cheaper to update the ERP than to build bridges to a decade-old version. Check that at the start, not halfway through.
Traps from real rollouts
Sync frequency - stock once a night is too rare with fast rotation: overselling guaranteed. Ask about the real interval and about what happens when the last unit sells simultaneously in two channels. Unit and variant mapping - the ERP thinks in cartons and item codes, the store in units and colour variants; bad mapping breeds phantom products. VAT and price groups - a drift in rates or in net versus gross prices only comes out on the invoices. Returns - they have to come back into stock in the ERP through the same pipe they left by; manual corrections pull the warehouse apart within weeks.
What helps: roll out flow by flow, not “everything at once”: stock first (the biggest gain, the smallest risk), then orders, and prices and products last. After each stage, a week of observation on live traffic. A big-bang integration switched on in full on a Friday is the classic recipe for a weekend with a broken warehouse.
Frequently asked questions
What does integrating a store with an ERP cost? It depends on the route: an off-the-shelf connector with a rollout is the cheapest, a setup with a sales integrator means subscriptions plus configuration, a bespoke build costs the most. I give the exact figure after looking at the store and the ERP - what decides it is the number of flows, the ERP version (and whether it has an API) and the state of the data. The main hidden cost is tidying up the data in the ERP - item codes, duplicates, units.
I have a store and an ERP and we retype everything by hand - where do I start? With stock synchronisation. It is one arrow, the biggest relief and an immediate end to overselling. The remaining flows come in stages.
Does this work for B2B too? It works ABOVE ALL for B2B - per-customer price lists and credit limits quickly become fiction without an ERP as the source of truth. The store-side layer of that setup I described in the piece on wholesale price lists.
Running a store where something does not work the way it should? I build and rebuild WooCommerce stores - from a single fix to reworking the whole sales flow. Tell me what you are dealing with and I will send back a scope and a price.