Sync online store inventory with your ERP: how to keep them equal

Your online store says “in stock”. A customer orders. There’s nothing in the warehouse. Or the other way round: the store says “sold out” and the shelves are full. Both cost you revenue and trust.

The solution in one sentence: let one system own the inventory, and send every change to your online store automatically. How to do that, and where it usually goes wrong, you’ll read below.

Why the inventory doesn’t add up

There’s almost always more than one place where inventory is kept. The ERP, the WMS, the online store itself, sometimes a marketplace too. As soon as two systems each have a stock level, they drift apart. These are the causes I see most often.

• Updating by hand. Someone copies the stock levels over every morning. Anything that sells or comes in between is missed.
• Syncing too slowly. Once a night is not enough for products that sell fast.
• Returns. A return comes back into the warehouse, but not into the online store.
• Multiple sales channels. Your online store and bol.com sell the same last item.
• Multiple warehouses. The online store adds everything up, while part of it is reserved or at another location.
• An integration that has stopped. After an update of one of your systems, the exchange stops. Nobody notices until a customer calls.

One owner of the inventory

The most important choice is which system holds the truth. In most businesses that’s the ERP or the WMS, because that’s where purchasing, receiving and picking happen. The online store then only shows what that system says, and never changes anything itself.

Does the online store sell something? Then the order goes to the ERP, the ERP lowers the stock and sends the new level back. Not the other way round. That way only one stock level can exist.

	Online store keeps its own inventory	ERP or WMS is the owner
Source	Two stock levels that drift apart	One stock level, the rest follows
Returns	Corrected by hand in the online store	Processed in the warehouse, online store follows
Multiple channels	Each channel counts its own inventory	One inventory, divided across the channels
On an error	You only see it when a customer calls	The integration reports it

How often to sync?

As often as needed, not as often as possible. For most wholesalers, every few minutes is enough. Do you sell few units of an item, or sell through multiple channels at once? Then you want to update immediately on every order and every receipt.

A standard extra step is a buffer. You show the online store one or two units fewer than are on the shelf. That way the last item isn’t sold twice in the minutes between two updates.

Multiple warehouses and channels

This is where it most often goes wrong at wholesalers. A few rules that work:

• Track per location, and decide per channel which locations count.
• Don’t show reserved stock. What’s already allocated to an order is no longer available.
• One allocation rule for your channels. For example: bol.com never gets more than half of the available stock.
• Include purchase orders. You can show expected receipts as a delivery time, not as stock.

Off-the-shelf connector or custom integration?

Honest advice. Do you have one online store, one ERP and no special rules? Then a ready-made connector does this fine, often for a few tens of euros a month.

A custom integration pays off as soon as you work with multiple warehouses, sales channels or entities, or when errors must not go unnoticed. Then you want an integration that follows exactly your rules and sends an alert when something stops. More on that in Integrating your online store and ERP. What a wholesaler needs to know.

How do you start?

Write down where inventory is kept today, how often it’s updated and where it went wrong in the last month. That’s all you need for a first call. You’ll hear right away whether an off-the-shelf app is enough, or whether custom work makes sense.