WMS integration with Shopify: where do things usually go wrong?

1. Stock synchronisation falls behind

The basic model is that the WMS passes stock levels to Shopify. At low volumes, this works well enough. At high volumes (say, more than 200 orders per day), delays start to appear. A customer purchases a product that has just sold out, and you are left with an empty shelf.

What most parties do not tell you: you need a buffer strategy. Either release stock only once an order has been picked, or hold back a safety stock of a few per cent. Which approach works best depends on your conversion rate and your returns percentage.

2. Variants and bundles are overlooked

Shopify thinks in products; the WMS thinks in SKUs. A variant with multiple sizes or colours means multiple SKUs. A bundle (a Christmas hamper, for instance) is a single product in Shopify, but three to five items picked together in the WMS.

Never let a migration go live without running test orders through variants and bundles. We have seen clients who only discovered after a week that their bundles were being dispatched as individual items.

3. Returns receive too little attention

Shopify has a returns API, but most tutorials skip straight past it. The result: stock that physically comes back sits at zero in the system. Or worse, at minus one.

A proper integration makes returns visible in both systems, with automatic stock correction as soon as the parcel arrives at the warehouse and the QC step has been completed.

4. Shipping labels are not where things go wrong

Most people assume the shipping label step is the tricky part. In practice, it rarely is. What tends to go wrong instead is this: the label is created, but the tracking information does not automatically feed back into Shopify. The customer receives no dispatch email, or an email with a broken link.

How we approach it

For every Shopify integration, we work through the four points above in advance. We build a test-order set covering four scenarios: a standard product, a variant, a bundle, and a return. Only once all four are correct in both systems does the integration go live.