Amazon inventory management for multi-channel brands

Keep FBA stock and own-warehouse stock as separate locations in one ERP, and let every sales channel read from it. Amazon orders and webshop orders then write back to the same stock record, so nobody reconciles counts by hand. That setup is the core of amazon inventory management for brands that also run a Shopify or WooCommerce store.

The general rules of multi channel inventory management apply to every channel. Amazon adds two twists: Amazon holds part of your stock, and Amazon fees punish both too much and too little of it.

This guide covers the stock pools to track and the Amazon fees that tie up cash. It ends with a five-step sync routine and how Prim.io connects Amazon to your webshop.

What is multi-channel Amazon inventory management?

Multi-channel Amazon inventory management is one stock record that covers Amazon FBA units and the warehouse stock your webshop shares with FBM. Every channel sells from that record, and every sale reduces it.

Most brands start with separate tools instead. Seller Central shows FBA units, while Shopify or WooCommerce keeps its own count of warehouse stock. Each order changes one count and leaves the other one stale.

Many Amazon inventory management software tools focus on the Amazon side, such as listings and restock alerts. An ERP adds the webshop, purchasing and finance to the same record. The method for calculating sellable stock across channels is in the hub guide linked above, so this guide stays on what Amazon changes.

How do FBA and FBM stock tracking differ for growing brands?

FBA stock tracking depends on Amazon's count of units held in its fulfillment centers. FBM stock tracking depends on your own warehouse count, and that same stock also feeds Shopify or WooCommerce.

That split means your FBA and FBM stock live in different places with different owners. Inbound stock adds a third pool that nobody can sell yet. The table shows how each pool behaves.

Stock pool	Who holds it	Who ships orders	Channels that can sell it	Main risk
FBA stock	Amazon fulfillment centers	Amazon	Amazon, plus off-Amazon orders through Multi-Channel Fulfillment	Storage fees on slow units
Own warehouse stock (FBM and webshop)	You or your 3PL	You or your 3PL	Amazon FBM, your webshop and other marketplaces	Overselling when channels share it
Inbound stock	Supplier, freight or Amazon receiving	Nobody yet	None until received	Counted too early or too late

Amazon's Multi-Channel Fulfillment service lets FBA inventory fulfill orders from off-Amazon channels, including your own website, from one shared pool. If you use it, your ERP must count those webshop orders against the FBA location. If you don't, keep FBA stock off the webshop entirely.

Amazon FBA vs FBM stock management tips

Amazon FBA vs FBM stock management works best when each pool has its own rules for buffers and replenishment. The four tips below apply those rules to day-to-day stock:

Send fast-selling SKUs to FBA and keep slow or bulky SKUs on FBM, so storage fees land only on stock that turns.
Hold a webshop buffer in your own warehouse before you push FBM quantities to Amazon.
Keep an FBM offer ready on top SKUs, so warehouse stock can cover Amazon demand when FBA runs low.
Review FBA counts and warehouse counts in one shared weekly report.

Why do multi-channel brands struggle with Amazon inventory?

Multi-channel brands struggle with Amazon inventory because Amazon's native tools track Amazon stock, and webshop tools track webshop stock. Nothing bridges the two by default, so units end up in the wrong place: cancelled orders on one channel, idle stock on another.

Amazon charges for both mistakes. An aged inventory surcharge applies to inventory stored longer than 181 days, on top of monthly storage fees. A low-inventory-level fee applies when historical days of supply falls below 28.

You can't fix a shortage by shipping everything to Amazon at once, either. Amazon sets inbound restock limits based on past and forecasted sales, and storage limits depend on your IPI score. So the buffer between too much and too little is narrow, and it moves with your sales.

Here is how that plays out, with example numbers. You hold 600 units of one SKU: 300 at FBA and 300 in your own warehouse. Your Shopify store reads the full 600 from a spreadsheet total.

A promotion sells 300 units across Shopify and FBM in one week. Every webshop order after that is a cancellation, because the remaining 300 units sit at Amazon. If Amazon sales are slow, those 300 FBA units also age toward the surcharge.

Neither problem shows up until someone reconciles the spreadsheet. By then, customers have received cancellation emails and cash sits in an Amazon warehouse.

Why do brands selling on Amazon and Shopify need centralized inventory?

Brands selling on Amazon and Shopify need centralized inventory because one stock record removes the reconciliation step. Each channel reads the same numbers, so the 600-unit example above would show 300 sellable units on Shopify from day one.

Centralized inventory also connects stock to cash. When FBA stock and open purchase orders sit in the same system as warehouse stock, finance sees how much money is tied up at Amazon. Purchasing sees what is already on the way before ordering more.

The model holds at scale. Maxxmart manages 30 legal entities and 50+ retail stores on one system. Multi-company setup matters for Amazon sellers who run a US company and an EU company side by side, each with its own books and stock.

For the webshop side, the Shopify ERP guide explains which jobs stay in Shopify and which move to the ERP. Amazon then becomes one more channel on the same record.

How do ERP integrations handle marketplace orders and stock?

ERP integrations handle marketplace orders and stock in two directions. Orders come into the ERP through a connector, and stock quantities go back out to each channel. Amazon FBA stock sits in the ERP as its own warehouse location.

In Prim.io, native integrations support marketplaces like Amazon FBA/FBM, eBay, Etsy, and webshops like Shopify and WooCommerce. The full list is on the Prim.io integrations page. Brands selling in the US and EU can run Amazon next to eBay and Etsy on the same product records.

How often stock updates reach a channel depends on the connector and on the channel's own rules. Check those connection requirements for each marketplace before you rely on them for a launch or a promotion.

What is the best way to sync Amazon and ecommerce stock?

The best way to sync Amazon and ecommerce stock is to give FBA its own location. Only own-warehouse stock should feed FBM and your webshop. The five steps below apply that rule to Amazon, and the general sync method is in the hub guide.

Create a separate FBA location in the ERP, with one location per region if you sell on Amazon in both the US and the EU.
Map every ASIN and seller SKU to one product record, so an FBA unit and a warehouse unit count as the same item.
Push only own-warehouse stock to Amazon FBM and to Shopify or WooCommerce, and keep FBA stock off the webshop unless you use MCF.
Plan inbound shipments to FBA from purchase orders, sized to your Amazon restock limits.
Review FBA and warehouse stock weekly in one report, and move units before they age or run short.

Step 3 is the one that prevents the cancellations in the earlier example. If your webshop runs on WooCommerce, the WooCommerce ERP integration guide covers the connection steps.

How Prim.io handles Amazon and webshop inventory

Prim.io is a cloud ERP with built-in AI for ecommerce and multi-channel brands, running orders, stock, finance, CRM, production and BI in one system. For Amazon sellers, Prim.io keeps FBA stock and own-warehouse stock as separate locations on one product record.

The Prim.io AI assistant answers stock questions from your own sales and stock data. Ask how many units sit at FBA versus your warehouse, and the answer comes from the same record your channels sell from.

Amazon connects through the Amazon FBA and Amazon FBM connectors listed on the integrations page, and Shopify and WooCommerce connect the same way. Marketplace connectors are paid add-ons at €50 per month. Webshop connectors cost €30 per month each, and plan details are on the Prim.io pricing page.

Inventory in Prim.io tracks bins, batches, serial numbers, expiry dates and barcodes, so FBA prep and warehouse picking use the same item data. More detail is on the cloud ERP for ecommerce page.

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Why ecommerce brands choose Prim.io

Ecommerce brands choose Prim.io for its AI assistant on top of an all-in-one ERP, BI and CRM built for ecommerce. Each part works from the same stock and order data, so no channel needs its own spreadsheet:

The AI assistant reads supplier invoices and matches payments, so finance spends less time on manual entry.
BI powered by Qlik puts Amazon margins and webshop margins side by side in one dashboard.
Purchasing, landed cost, manufacturing with BOMs and multi-warehouse stock run in the same system as channel stock.
Multi-company setup handles several legal entities, as the Maxxmart example above shows.
Prim.io processes 3.1M+ orders every month through 50+ native integrations and an API.

Amazon inventory management FAQ

The Amazon inventory management FAQ below answers short questions on syncing stock and on Prim.io costs. Each answer stands on its own.

How do I sync Amazon and Shopify stock?

Sync Amazon and Shopify stock by connecting both channels to one ERP that holds a single product record per SKU. Keep FBA units in their own location, and push only own-warehouse stock to Shopify and Amazon FBM. Check each connector's update frequency before a promotion, and review both stock pools in one weekly report.

What is the cost of marketplace connectors?

Marketplace connectors are the highest-priced connector type in Prim.io, sitting at the top of the range below. Store, marketplace and courier connectors are priced per connector (€20 to €50 per month); finance connectors are free. Webshop connectors cost €30 per month and courier or 3PL connectors €20 per month, on top of the plan fee.

Can Prim.io manage Amazon FBA and FBM?

Yes, Prim.io manages Amazon FBA and FBM through the Amazon FBA and Amazon FBM connectors listed on the integrations page. FBA stock sits in its own location, and FBM orders ship from your warehouse stock. Each connector has a monthly fee, so check connection requirements for your Amazon marketplaces before you scale to new regions.

How does Prim.io connect Amazon and webshop inventory?

Prim.io connects Amazon and webshop inventory by mapping every Amazon seller SKU and webshop SKU to one product record. Amazon orders and Shopify or WooCommerce orders all reduce stock in that record. Purchasing then plans replenishment for FBA and your own warehouse from the same numbers, so neither pool runs short unnoticed.

How much does Prim.io cost?

Prim.io costs a fixed monthly fee per plan, with connectors priced separately. Prim Plus is €180, Prim Pro €540 and Prim Enterprise €1,710 per month, billed annually, excluding VAT, with 3, 5 and 15 users included. You can test the system before choosing a plan with a free demo account.

Checklist for Amazon and webshop inventory

Amazon and webshop inventory stays aligned when you run one stock record and review it every week. Run through the checklist below before you add your next channel:

Map FBA, FBM and webshop stock into one control center.
Replace manual spreadsheet updates by integrating every channel into an ERP.
Track purchasing and inbound shipments to keep stock buffers at FBA and in your warehouse.
Review multi-channel sales with built-in BI powered by Qlik.
Check marketplace connection requirements before you scale to new channels.