Marketplace integration in the UK: how it works and what drives the cost

A customer buys from you on Amazon at nine in the morning. By ten, that order should be in your stock system, booked for despatch and ready to invoice, with nobody retyping it. Closing that gap takes a connection, not another login.

What is marketplace integration and how does it work?

Every marketplace has its own way of receiving and sending data. Amazon, eBay, TikTok Shop and the marketplaces built on Mirakl each publish their own interfaces, with their own rules for what an order, a despatch confirmation or an invoice looks like. Integration is the translation layer between those rules and your own ERP, warehouse or accounting system.

In practice a connected order follows four steps:

1. A customer orders on the marketplace.
2. The order is translated into the format your system expects and routed straight in.
3. Despatch and invoice data go back out to the marketplace in the format it requires.
4. Every message is monitored, so a failed order is spotted and fixed before it costs you a sale.

The connection itself can run over an API, over EDI (Electronic Data Interchange, the standard electronic exchange of orders, despatch advices and invoices between trading partners) or over file feeds. GS1 describes its EDI standards as electronic business messaging that automates transactions across the supply chain, from orders and delivery to financial settlement. Wayfair's own seller guidance puts the difference plainly: its API exchanges order and inventory data in real time, while EDI exchanges it at regular intervals and asks less of your technical team. Which one you need is set by what each marketplace supports.

Which marketplaces matter most to UK sellers?

The marketplaces below are the ones UK sellers ask about most. Each is described from its own documentation, and the connection options differ more than the sales pages suggest.

Amazon: Seller Central and Vendor Central

Amazon runs two models. Seller Central is where third-party sellers manage their own listings, stock and orders, and any eligible business can register. Vendor Central is the wholesale model, where you supply Amazon in bulk and Amazon sells to the customer, and it is by invitation.

Within Seller Central you choose who fulfils. With Fulfilment by Amazon, Amazon stores the stock and packs and ships the order. With Fulfilled by Merchant, you do. Separately, Amazon's Direct Fulfillment programme is for vendors: Amazon sends you a purchase order, you pack and ship the goods, and you return a shipment confirmation and an invoice. Amazon's guide says a Direct Fulfillment purchase order can be confirmed through its API, through Vendor Central or through EDI.

Amazon also restricts personal data in orders. Only applications it has reviewed and approved can receive buyer details such as delivery addresses. Transalis is a certified Amazon Selling Partner, which means it can handle that data on your behalf and pass it to your logistics or EDI chain without a manual step. If your question is specifically about Seller Central and EDI, our guide on whether EDI is available for Seller Central goes further.

eBay

eBay publishes an Inventory API and a Fulfillment API that cover listings and order handling, and it also offers a feed-based route for bulk uploads. The interface exists, but somebody still has to build, secure and maintain the connection to your stock system. See how Transalis handles the eBay connection.

TikTok Shop

TikTok Shop has a dedicated UK seller site, and its Partner Center publishes developer documentation covering orders, products and fulfilment. Most of what you will find online explains how to open a shop and link an account. The harder question is how TikTok orders reach your ERP, warehouse or order management system without somebody copying them across. That is the part a connection handles, and it is covered on the TikTok Shop integration page.

Mirakl-based marketplaces

Mirakl supplies the technology behind many retailer-run marketplaces, where third-party sellers list products and the retailer takes a commission. Mirakl says sellers can connect by API, CSV, XML, EDI or SFTP. B&Q Marketplace is one example: Mirakl announced its launch in March 2022. The practical point for a seller is that two retailer marketplaces may share a technology and still differ in the catalogue and order rules you must meet.

Walmart, Wayfair and others

Walmart is recruiting UK sellers, but to its marketplaces in the United States, Canada, Mexico and Chile, not to a UK marketplace. Wayfair offers both an API and EDI to its suppliers, and our Wayfair and the digital era case study covers how one supplier, Simplehuman, connected to Wayfair and its other trading partners with EDI. OnBuy and Etsy each publish their own seller APIs too. Transalis connects to the marketplaces listed on its marketplace connectivity page, which as of October 2026 names Amazon, eBay, TikTok Shop, Mirakl, B&Q Marketplace, Zalando, Wayfair, Walmart Marketplace and Shopify. Shopify merchants can see how Transalis connects Shopify to trading partners.

Channel manager or managed marketplace connectivity?

A channel manager is software you log into and run. It is built to publish listings and keep stock levels in step across channels, and it does that job well. Where it usually stops is the document flow behind the sale: getting each order into your ERP in the right format, sending the despatch confirmation back, raising the invoice, and chasing the order that failed overnight.

Managed marketplace connectivity is the outcome rather than the tool. The provider connects the channels, translates the formats, watches every transaction and fixes errors, so there is no dashboard for your team to operate. The two are not rivals for every seller. If listing and pricing is your daily work, a channel manager earns its place. If the pain is orders, despatch and invoices landing in your systems accurately, you are describing a connectivity problem.

A DIY build gives you the most control and the longest to-do list. You write each connection, secure it, and rework it whenever a marketplace changes its rules. Teams with spare engineering capacity sometimes choose this for one or two channels, and every extra channel adds to the list.

Can you sell on marketplaces and supply supermarkets from one system?

Yes, and this is where managed connectivity differs most from a marketplace-only tool. Many sellers run two projects: one set of connections to sell on marketplaces, and a separate EDI arrangement to supply the supermarkets and retailers that require it. That means two integrations, two suppliers and two things to break.

The Transalis Trading Network removes the split. It connects 15,000+ organisations, so the connection that carries your Amazon orders also reaches Argos and the UK's grocery retailers. Most of the retailers that mandate EDI are already on the network, so you join once rather than building a link to each buyer.

Behind the order flow, the Integrations Network plugs that single connection into the systems you already run, so a change of ERP or a new channel does not mean starting again. Transalis DataTrack™ shows every message in real time, and the managed team resolves problems before they touch your trading.

What drives the cost of marketplace integration in the UK?

Costs vary too much between sellers for a published figure to be useful, and any number quoted without knowing your channels and systems would mislead you. What you can compare reliably is what moves the cost. Six drivers matter, and they apply whichever route you choose.

The pricing model deserves the most attention. A per-order or per-message charge turns every sales win into a bigger bill, which is a penalty for growing. Transalis works on predictable, fixed-cost packages instead, with no per-order fees and no charge that grows each time you sell more. Setup and partner mapping is a one-time fee priced by the number of trading partners you connect, integration is a one-time fee scoped to your systems and workflows, and the monthly subscription is flat, with no per-message metering. Talk to us and we will map the right package to your channels.

How do I automate orders from Amazon, eBay and other marketplaces?

Start by listing every channel and the documents each one needs. Then decide who owns the connection. If you build it, every marketplace change lands on your team. If a managed provider owns it, the order, despatch and invoice flow runs without you touching it.

Seven questions are worth asking any provider, or your own team, before you commit:

1. Which of my marketplaces are live today, and which are planned?
2. Does the connection reach my ERP, or only my storefront?
3. Who handles it when a marketplace changes its interface?
4. How are failed orders found, and who fixes them?
5. Does the same connection reach the retailers I supply by EDI?
6. How is the price built, and what grows it as I sell more?
7. How long does a new channel take to add?

For Transalis, a new marketplace is a matter of days rather than months, because the managed team handles the connection, mapping and testing. For more on connected channels, read why connected marketplaces matter for D2C food and beverage sales in the UK, or our checklist for dropshipping and marketplace suppliers.

Ready to connect your marketplaces?

If you sell on more than one channel and still copy orders between screens, the quickest next step is a conversation about which channels and systems you run. Connect your marketplaces to see how the managed model works, or book a meeting and we will map the connections with you.