OnBuy Inventory Management: How to Sync Stock Across Channels (UK)

Why OnBuy is worth taking seriously

OnBuylaunched in 2016 and has grown steadily to become one of the UK's most credible eBay alternatives. Unlike Amazon, OnBuy doesn't compete with its own sellers — it has no own-brand products and doesn't run a retail arm. Every sale goes to a third-party seller.

The platform runs regular cashback promotions for buyers, which drive strong conversion rates for sellers. Commission rates vary by category (typically 5–9%) with no listing fees and no monthly subscription required to sell.

For UK sellers who already operate on eBay or Amazon, OnBuy is a natural addition — same products, different audience, additional revenue with minimal extra work. The problem is that "minimal extra work" assumption quickly breaks down once you're managing stock across three or more platforms.

OnBuy's built-in stock management

OnBuy gives you quantity fields on each listing. You can set stock levels, and OnBuy will mark a listing as out of stock when quantity hits zero. That's essentially it.

There's no multi-channel awareness. OnBuy has no way of knowing that the same product is also listed on eBay or your Shopify store — so when a sale happens elsewhere, your OnBuy quantity stays unchanged until you manually update it.

For low-volume sellers with a small catalogue, manual updates are manageable. At any kind of scale — especially during peak selling periods — they're a disaster waiting to happen.

The OnBuy + eBay overselling problem

A typical scenario: you have 4 units of a product. You list all 4 on both OnBuy and eBay. Three sell on eBay on a busy Saturday afternoon while you're out. OnBuy still shows 4 available. A buyer purchases 3 on OnBuy that evening. You've now sold 6 units of something you only had 4 of.

Now you have two options: cancel one of the OnBuy orders (damaging your seller metrics and leaving an unhappy customer), or scramble to source the product at short notice — likely at a loss.

This scenario plays out thousands of times a day across UK marketplace sellers. It's not a rare edge case — it's the predictable result of managing inventory manually across multiple platforms.

OnBuy vs eBay: which is better for UK sellers?

For most UK sellers, the answer is both. OnBuy's lower commission rate and cashback-driven conversion complement eBay's massive audience. Running both in parallel — with the right inventory software — adds meaningful revenue with very little additional overhead.

How to sync OnBuy with your other channels

The solution is a central inventory system that treats all your channels — OnBuy, eBay, Amazon, Shopify — as outputs of the same stock pool. When a sale happens anywhere, the system:

1. Detects the sale on the originating platform
2. Deducts the quantity from your central stock count
3. Pushes the updated quantity to all other connected channels simultaneously

With Salync, this happens in real time. Connect your OnBuy account alongside eBay, Amazon, or Shopify, and stock levels stay accurate across all of them the moment a sale lands anywhere.

Tips for OnBuy sellers going multi-channel

Use SKUs consistently across platforms

OnBuy, eBay, and Amazon all have fields for a seller SKU or reference code. If you use the same SKU for the same product across all platforms, inventory software can link them automatically. If your SKUs differ between platforms, you'll spend time manually mapping listings. Set a consistent SKU convention before you expand — it saves significant time later.

Set a stock buffer

Even with real-time sync, a buffer of 1–2 units per channel is worth having. It protects against edge cases: a return in transit, a stock count discrepancy, or a brief lag between a sale and the sync firing. Most sellers set a buffer of 1 and rarely see it matter — but on the occasions it does, it saves an oversell.

Keep your listing titles platform-appropriate

OnBuy titles follow similar conventions to eBay — keyword-rich, descriptive, up to 80 characters. If you're copying listings from eBay to OnBuy, they'll usually transfer well. If you're coming from Amazon, your titles may need trimming — Amazon allows longer titles with more keyword stuffing than OnBuy buyers expect.

Monitor your OnBuy performance metrics

Like eBay, OnBuy tracks seller performance. Late despatch, order cancellations, and negative feedback all affect your visibility on the platform. Keeping inventory accurate — so you're never cancelling orders because you're out of stock — is one of the most direct ways to protect your seller status.

Common questions about OnBuy inventory management

Does OnBuy integrate with inventory software?

OnBuy has an API that allows inventory management software to read and update listing quantities. Tools like Salync use this API to sync stock between OnBuy and your other channels in real time. No manual exports or uploads required.

Can I manage OnBuy and eBay stock in one place?

Yes — with multi-channel inventory software. Salync connects to both OnBuy and eBay, so you manage one central stock count and let the software keep both channels updated automatically. You can see all your channel stock in one dashboard and make bulk adjustments without switching between platforms.

What happens if OnBuy goes out of stock?

When your quantity on OnBuy hits zero, your listing is automatically marked as out of stock and hidden from buyers. When stock is received and your quantity is updated (either manually or via your inventory software), the listing goes live again. OnBuy doesn't charge listing fees for out-of-stock periods.