Integrating WooCommerce with Subiekt GT: five things that only show up in practice

An online shop selling oils, filters and consumable parts: 1,800 products on WooCommerce, around 40 orders a day, stock and invoicing in Subiekt GT. Before the integration it worked like this: every morning Ewa printed the orders from the shop and issued invoices for them in Subiekt, one after another. Forty invoices is about two hours. She updated stock levels in the shop once a day from an export, so for the rest of the day the shop was sometimes selling things that were already gone.

The plan was eight days. It took eleven, and those three days are the subject of this post, because every shop-to-ERP integration I've done has had its own versions of the same five problems.

How it's wired up

Subiekt GT has no API of its own; you need the Sfera add-on from InsERT, which lets a script talk to the program. On the shop side there's the standard WooCommerce REST API. In between sits n8n with a few scripts on the client's server. Every two minutes it pulls new orders into Subiekt and pushes stock levels to the shop, once an hour it syncs prices and new products, and on a status change it issues the invoice and sends its number back to the order in the shop.

Sounds simple. For the first four days it was simple.

Surprise 1: one grosz

Day five, the first invoices from the automation. The accountant rings: invoice for PLN 123.46, transfer for PLN 123.45, order marked "unpaid" in Subiekt. A one-grosz difference (a grosz is a hundredth of a złoty) in 7% of orders.

WooCommerce calculates prices from gross and rounds the total. Subiekt by default calculates from net, line by line, and rounds each line separately. With three units at 41.15 the result differs. The solution is to pass gross prices to Subiekt with "calculate from gross" set on the document, exactly the way the shop does it. One field in Sfera and half a day of finding out why.

Surprise 2: the last unit sold twice

Day six. Two customers bought the same filter two seconds apart, and there was one unit in stock. The shop accepted both orders, because the last stock sync had been two minutes earlier. Both paid.

You can't get a full guarantee here without rebuilding the shop, but you can get the risk down to almost zero. An order creates a reservation in Subiekt the moment it's placed, and for the 60 best-selling products stock goes to the shop every 30 seconds instead of every two minutes. In the two months since that change there hasn't been a double sale. There was one case where the item turned out to be damaged on the shelf, but no integration will catch that.

Surprise 3: statuses

The shop has five order statuses; Subiekt has documents: ZK (a customer order), FS (a sales invoice), WZ (a goods issue note), corrections. We agreed the mapping on day four and it seemed obvious.

On day nine a customer placed an order and an hour later changed the delivery address through their account in the shop. The order was already in Subiekt with the first address, so the WZ and the courier label went to the old one. The parcel came back. Now the address goes to Subiekt only when the status changes to "Completed", that is, when someone is actually packing, and the integrator checks whether the address in the shop has changed since the ZK was created.

Surprise 4: an emoji in the notes

The "order notes" field. A customer wrote "please leave it with the neighbour 🙏". Sfera accepted it, Subiekt saved it, and when printing the WZ an error popped up, because that version can't handle such characters. Three orders sat in the queue before anyone noticed. Now the integrator strips the notes of characters outside the Polish alphabet, and the original stays in the shop. A small thing, but exactly the kind of thing that's in no documentation and only shows up on real orders.

Surprise 5: returns

A return in the shop is the "Refunded" status; in Subiekt it's an invoice correction plus receiving the goods back into stock. For the first two weeks Ewa did the corrections by hand, because we wanted to see what real returns look like first: partial, with an exchange, "return, but the customer wants a different oil". The automation now handles full returns. Partial ones still get a draft correction to click through, and that's deliberate, because there are six a month and each one is different.

After two months

Efekt: Zero invoices issued by hand (it was around 40 a day). Shop stock lags by 30 seconds for the hot products and two minutes for the rest. Ewa now writes the product descriptions the shop had been missing for two years. I can't honestly count the sales, because the shop started running ads at the same time, but returns due to "it wasn't in stock" dropped from a dozen or so a month to zero.

Before you order an integration

Check whether you have Sfera (or Subiekt nexo, which has an API as standard). See how the shop calculates VAT and set the same in Subiekt. Plan two or three days for surprises, because there will be some. I've had them every time, and this was my sixth integration of this kind.