How to Prepare Your Online Store for Multichannel Selling — a Step-by-Step Checklist

Adding another sales channel — a marketplace next to your own store, a second marketplace, or cross-border sales — can multiply your turnover. It can also multiply the chaos if you launch without preparation. The most common failure looks like this: you connect a second channel “in a hurry”, and two weeks later you have overselling, mismatched SKUs and statuses nobody can follow. The problem isn’t the channel — it’s that the store wasn’t ready.

The good news: preparation is a checklist to work through, not magic. This guide gives you a step-by-step list — from cleaning up your catalog and SKUs, through one warehouse and clear processes, to choosing channels, integrations and testing. Work through it before you launch on new channels, and multichannel growth stops being a lottery.

Step 1: Clean up your catalog and SKUs

The foundation of multichannel selling is a consistent product catalog. It’s the link every channel uses to recognize the same physical unit. If the catalog is a mess, no integration will fix that — it will only spread the error across every channel at once.

To check off:

• One SKU = one physical unit. Every product and every variant (size, color) has its own unique code. No duplicates, no “temporary” codes.
• SKUs at the variant level, not just the product. If you sell shirts in three sizes, you need three SKUs — otherwise stock won’t deduct correctly.
• A naming convention. Set a readable code scheme (e.g. category-model-variant) and stick to it for every new product.
• Remove dead entries — discontinued products, duplicates, test items. The cleaner the catalog, the less work mapping it onto channels.
• Fill in the data — titles, descriptions, images, EAN/GTIN. Gaps you tolerate today in a single store will block you from listing on a marketplace.

This is the most labor-intensive and, at the same time, the most important step. Messy SKUs are the number-one cause of overselling — spend as much time on it as it takes.

Step 2: Set one shared warehouse

The second pillar is a single source of truth for stock levels. As long as each channel counts availability its own way, overselling is only a matter of time — a customer buys the last unit on one channel while another still shows it as available.

To prepare:

• Designate central stock — one place that holds the truth about quantity, with channels as consumers of that information.
• Sync stock levels at the start — before you connect another channel, make sure the numbers in the catalog match the physical shelf. An integration spreads exactly what you feed it.
• Plan reservations — “available to sell” is not the same as “on the shelf”. An order that’s paid but not yet shipped should hold the unit.
• Set an update frequency — with higher traffic an hourly cycle isn’t enough; aim for near-event-driven synchronization.

The topic is important enough that we’ve covered it separately — see how Allegro and WooCommerce inventory sync works.

Step 3: Define your order-handling processes

More channels means more orders that must pass through the same, repeatable process. Before you multiply them, unify the workflow — otherwise each channel will generate its own exception.

• A shared status dictionary — new → paid → in progress → shipped → completed (plus canceled and returns). Map every channel’s statuses onto this single set.
• A clear fulfillment path — who packs, who ships, who handles returns. The process must be independent of the channel an order came from.
• Priority rules — what you pack first, how you treat express orders.
• Exception handling — stockouts, cancellations, complaints. Settle it now, calmly, not during a sales peak.

If you want a ready workflow skeleton, we’ve described it in a separate post on a simple order fulfillment process.

Step 4: Choose channels deliberately

Don’t go everywhere at once. Each channel is a separate workload — different product-data requirements, different commissions, different logistics. It’s better to serve two channels well than five badly.

When choosing the next channel, ask yourself:

• Does my assortment fit this channel and its customers?
• What are the commissions and costs, and can my margin carry them?
• What product data does it require (categories, parameters, EAN)?
• Who on my side will handle the support and shipping for the extra volume?

For many sellers the natural pair is their own store + a leading marketplace, with the next steps being a global marketplace or cross-border sales. Go in stages, learn on one channel, then replicate.

Step 5: Connect integrations and test

Once your catalog, warehouse and processes are ready, it’s time to tie the channels together — ideally through an OMS (Order Management System) that pulls orders and products from every channel into one normalized view. Instead of connecting each channel to every other, you connect them all to one hub.

Sellaro does exactly this: today’s ready modules are PrestaShop, Sylius and WooCommerce, while channels such as Allegro, Amazon or Shopify are on the roadmap and added on request as part of your plan (our rule: we add a missing integration for free). On top of that comes an automation engine on domain events (WHEN → IF → THEN) with actions: email (SMTP) and SMS notifications, webhooks (HMAC + retry) and a log entry.

An honest caveat: store integrations are READ-ONLY — Sellaro reads data from channels but does not write to the store (it doesn’t change orders, it doesn’t create listings). Generating courier labels and issuing invoices is a roadmap goal, not a feature that’s ready today.

Before you announce the launch, test at small scale:

• connect one new channel and check that orders arrive correctly mapped,
• place a test order and walk the whole path: stock deducts, status changes, notification goes out,
• verify the export (e.g. CSV to accounting) on real data,
• only after a successful test increase volume and add further channels.

Frequently asked questions

Where do I start when preparing for multichannel selling?

Start with the catalog and SKUs. It’s the foundation every channel uses to recognize the same product. Until codes are consistent and unique at the variant level, no integration will work properly — it will only spread the error to every channel.

How many channels should I launch at the start?

Start with two — usually your own store and a leading marketplace. One channel you can run in its own panel, but with two you already need a shared warehouse and statuses. Learn the model on two channels, then simply plug the rest into a ready hub.

Do I need every channel available as an integration?

No. In Sellaro, start with the ready ones (PrestaShop, Sylius, WooCommerce), while the missing ones — like Allegro or Amazon — are on the roadmap and added on request as part of your plan. You set up the shared warehouse and automation once, and new channels simply join.

How do I avoid overselling after adding a second channel?

Set one central stock level, based on consistent SKUs, and sync it as close to event-driven as possible. Also plan reservations so that an order that’s paid but not yet shipped holds the unit across all channels.

Summary

Multichannel selling works for those who prepared the store before they launched. The checklist is simple: clean up your catalog and SKUs, set one warehouse, define your order-handling processes, choose channels deliberately, and finally connect integrations and test at small scale. Every box you check is one less fire when volume ramps up.

Want the bigger picture? Read how to sell across channels without chaos, and then work out your cost — 0% commission on sales, all integrations included in your plan, and a missing one added for free.