Amazon FBM Inventory Tracking: A Complete Guide for Sellers

Selling through Amazon FBM (Fulfilled by Merchant) gives you full control, you store, pack, and ship your own products.

But with that freedom comes responsibility, and the biggest one is keeping your inventory accurate.

One wrong update can mean overselling, late deliveries, or penalties from Amazon.

If you’re also running a Shopify store, the challenge doubles, because every sale draws from the same stock pool.

In this guide, we’ll break down what FBM inventory tracking is, the common challenges sellers face, and how to keep your Amazon FBM and Shopify inventory perfectly in sync.

What Is Amazon FBM Inventory Tracking?

Amazon FBM (Fulfilled by Merchant) is when you, the seller, handle everything from storing products, packing boxes, and shipping orders, rather than letting Amazon do it for you through FBA.

That extra control comes with extra responsibility, and at the heart of it is inventory tracking.

FBM inventory tracking simply means keeping your stock counts accurate at all times.

Every sale, cancellation, or return needs to be reflected in your system so that what customers see on Amazon matches what you actually have in your warehouse or storage space.

Here’s why it matters:

• It protects you from overselling items you don’t have.
• It helps you avoid late shipments and the penalties that come with them.
• It keeps your seller metrics strong, which is crucial for staying competitive on Amazon.

Common FBM Inventory Tracking Challenges

Running FBM sounds straightforward, you keep stock in your own warehouse or office, update counts, and ship orders. But in practice, it quickly becomes a juggling act. Here are the most common pain points sellers run into:

• Overselling stock
  When inventory updates lag, customers may place orders for items you no longer have. This leads to cancellations, refunds, and unhappy buyers, plus potential penalties from Amazon.

• Sync delays across channels
  Many FBM sellers also list on Shopify, Etsy, or eBay. Without proper sync, a sale on one channel doesn’t immediately reduce stock on the others, creating mismatched numbers and risk of overselling.

• Returns and damaged goods
  Not every returned item can go back on the shelf. If you don’t separate re-sellable and unsellable items in your system, your available stock count becomes unreliable.

• Manual updates and human error
  Spreadsheets and manual edits feel manageable at first, but as you grow, a single typo can throw off stock counts across dozens of SKUs.

• No unified inventory view
  If your stock is scattered across multiple systems or fulfillment locations, it’s tough to know what’s truly available. This lack of visibility makes forecasting and planning nearly impossible.

How to Keep Amazon FBM and Shopify Inventory in Sync

To manage one shared stock pool across Amazon FBM and Shopify, sellers usually try three approaches. Each works at a small scale, but they come with trade-offs.

1. Manual Updates

Manually logging into both platforms and adjusting quantities after every sale.

✅ Pro: Free, simple to start with.

❌ Con: Easy to forget, slow, and unscalable once sales grow.

2. CSV Imports/Exports

Exporting stock data, adjusting it in spreadsheets, and uploading it to update inventory in bulk.

✅ Pro: Faster than manual edits, handles many SKUs at once.

❌ Con: Not real-time, data can already be outdated during busy sales.

3. Automated Sync Tools

Using apps like Sumtracker help you connect Shopify and Amazon FBM for instant, two-way inventory updates.

✅ Pro: Real-time accuracy, zero manual effort, scalable for growth.

❌ Con: Paid option, but far more reliable than manual or CSV methods.

How Sumtracker Simplifies Amazon FBM Inventory Tracking

Sumtracker removes the guesswork and manual effort from managing FBM inventory across Amazon and Shopify. Instead of juggling spreadsheets or worrying about sync delays, it gives you one reliable system to keep everything in check. Here’s how:

• Real-time two-way sync → Every sale, return, or restock updates instantly across Amazon FBM and Shopify, eliminating overselling.
• One central dashboard → Manage all SKUs from a single view instead of switching between multiple platforms.
• Accurate returns handling → Easily adjust stock when items come back, marking them as re-sellable or unsellable.
• Error-free updates → Automation removes the risk of typos, missed edits, or outdated CSV uploads.
• Scales with growth → Works just as smoothly for 50 SKUs as it does for 5,000, supporting long-term expansion.

With Sumtracker, FBM sellers spend less time fixing inventory issues and more time focusing on fulfillment and growth.

Conclusion

Amazon FBM gives you full control over storage, packing, and shipping but it also puts the weight of inventory accuracy on your shoulders.

From preventing overselling to managing returns and keeping Shopify in sync, the right system can make or break your success.

With Sumtracker, you don’t just track inventory, you stay ahead of it.

Real-time sync, a unified dashboard, and error-free updates mean fewer headaches, stronger seller metrics, and more time to focus on growing your business.

Ready to simplify FBM inventory tracking?

Try Sumtracker today and take the stress out of managing your Amazon FBM and Shopify stock.

FAQs

1. What is Amazon FBM inventory tracking?

It’s the process of keeping your stock counts accurate when you fulfill orders yourself, ensuring Amazon listings match your actual warehouse inventory.

2. Does Shopify sync directly with Amazon for FBM sellers?

No, Shopify doesn’t natively sync with Amazon FBM. You’ll need an inventory management tool like Sumtracker to keep stock accurate across both platforms.

3. How can I avoid overselling on Amazon FBM?

Use automated inventory sync tools that update stock in real time across Amazon FBM and Shopify, reducing errors from manual edits or delayed CSV uploads.

4. What’s the best way to manage FBM returns?

Always inspect returned items first. Mark re-sellable items back into inventory and adjust unsellable ones separately to keep counts accurate.

5. Is Sumtracker only for Amazon FBM and Shopify?

No, Sumtracker supports multiple sales channels including eBay, Etsy, and WooCommerce, giving sellers one centralized system to manage inventory everywhere.

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