How to Connect Allegro, WooCommerce, InPost and Invoicing in One System

A typical Polish store sells on Allegro and through its own WooCommerce shop, ships mostly with InPost, and has to issue invoices. Each of these pieces lives in its own panel, and connecting them means copy-pasting data all day long: the order number here, the address there, the label somewhere else, the invoice at the very end. The more orders you have, the more windows you juggle and the higher the risk of error.

This article shows how to design one system that ties together Allegro, WooCommerce, the courier and invoicing — and what to watch out for so the whole thing is coherent rather than a patchwork of plugins.

The problem: four panels, one process

Even though the tools are separate, the process is one: an order comes in, it needs to be picked, shipped and documented. Splitting that across four panels creates three costs:

• time — logging in and copy-pasting between Allegro, WooCommerce, the courier and accounting,
• errors — a typo in the address, the wrong label, an invoice with the wrong details,
• lack of visibility — you can’t see in one place what has been paid for, packed and shipped.

The solution is a central OMS (Order Management System) that becomes the single source of truth about an order, with the other systems plugged in as sources and recipients.

Layer 1: a central OMS as the heart of operations

At the heart of the setup is a system that gathers orders from every channel and carries them through the entire cycle. This is where orders from Allegro and WooCommerce land, where you see the status of each one, and from where you trigger both shipping and invoicing.

A good OMS normalizes data — an order from Allegro and one from your shop look the same, have consistent statuses and the same address format. As a result, the layers above (courier, accounting) don’t need to know which channel an order came from.

In Sellaro, orders and products from all connected channels land in a shared, normalized view, and the automation engine reacts to events (a new order, a status change) with “if this, do that” rules.

Layer 2: Allegro and WooCommerce as sales channels

The first step is connecting the order sources:

• WooCommerce — as a channel (a plugin or the shop’s API keys) from which the OMS pulls orders and products,
• Allegro — through account authorization (the Allegro REST API); multiple accounts are simply multiple channels in one shared queue.

It matters that products from both channels map by SKU — that lets you run one shared inventory and avoid overselling (we expand on this in a separate guide on inventory sync).

In Sellaro the WooCommerce module is ready, while the Allegro integration is on the roadmap and we add it on request — in line with our rule that we add a missing integration free of charge as part of the package.

Layer 3: inventory and shared stock

Since you’re selling the same goods across two channels, you need one shared stock level that decrements after every sale and reaches both channels before overselling happens. The central OMS is the natural place for such inventory: it knows about all the orders, so it’s the one that should watch stock.

For clothing or footwear, sync has to work at the variant level (size, color), not just the product. It also helps if the system reserves the item at the moment of the order rather than only at shipping.

Layer 4: InPost and other couriers

Once an order is paid and picked, it’s time to ship. The target setup is generating a courier label from the order data without retyping the address — for InPost, but also DPD, DHL or Orlen Paczka, since most stores use several couriers at once.

When designing this layer, pay attention to:

• automatic mapping of the delivery method from the order to the courier service,
• parcel lockers — for InPost the chosen point has to carry over from the order to the label,
• tracking — the shipment number should flow back into the order and (optionally) to the customer.

Courier integrations in Sellaro belong to the connectors we add as customer needs arise — if InPost is your main courier, flag it during onboarding.

Layer 5: invoices and accounting

The last piece is documents. Ultimately the invoice is created automatically once the order is paid, based on its data, and flows into your accounting system (e.g. Fakturownia, wFirma). This takes manual issuing off your team’s plate and eliminates errors in buyer details.

For this layer, check:

• timing of issue — after payment, after shipping or on demand,
• buyer details — correct transfer of the tax ID and address from the order,
• numbering — consistent and aligned with your accounting.

In Sellaro’s package model, accounting (Fakturownia/wFirma) is planned as a higher-tier distinguishing feature — a piece of the “one system” puzzle we’re building toward.

How to tie it together in practice — the rollout order

Don’t connect everything at once. A proven order:

1. Connect the OMS to WooCommerce and Allegro — first, gather orders in one place.
2. Sort out inventory — shared stock and sync, to stop overselling.
3. Add a courier — automatic labels for your main delivery method (e.g. InPost).
4. Turn on invoices — automatic issuing after payment.
5. Automate the rest — statuses and notifications to the customer.

Each step delivers measurable savings and can be launched on its own, without any risk of blocking your sales.

Frequently asked questions

Do I need separate tools for Allegro, WooCommerce, InPost and invoices?

No — it makes more sense to tie them around one central system (an OMS) that becomes the source of truth about the order, with the other systems plugged in as sources and recipients. That way you don’t copy-paste data between four panels and you see the whole process in one place.

Where do I start connecting these systems?

By gathering orders in one place: first connect the OMS to WooCommerce and Allegro, then sort out shared inventory, next add a courier (labels), and finally invoices and the remaining automations. Each step delivers a separate saving and can be launched independently.

Can InPost labels be generated automatically from an order?

That’s the goal of a well-arranged system — the label is created from the order data without retyping the address, and for parcel lockers the chosen point carries over from the order to the label. In Sellaro we add courier integrations as customer needs arise; flag InPost during onboarding.

Can invoices be issued automatically after an order?

Ultimately yes — the invoice is created once the order is paid, based on the order data, and flows into your accounting system (e.g. Fakturownia, wFirma). It’s important that it correctly transfers the buyer’s tax ID and address and keeps consistent numbering aligned with your accounting.

Summary

“One system” for Allegro, WooCommerce, InPost and invoices isn’t one magic plugin, but well-arranged layers around a central OMS: sales channels → shared inventory → couriers → accounting, tied together by automation. The key is a single source of truth about the order and gradually connecting the next pieces.

We’re building Sellaro as exactly that kind of hub — some integrations work today, more arrive as modules, and we add a missing one free of charge. See the current integration catalog and work out your cost in the pricing.