Kyle Moloney
Procurement & Operations | 10+ Years
Kyle has spent over a decade managing procurement and operations for manufacturing companies ranging from small food producers to mid-size contract manufacturers. He now writes about practical inventory management, supply chain, and production operations.
Two inventory truths, one spreadsheet trying to reconcile them
If you manufacture the products you sell on Amazon, you already know the split. Some of your stock sits in an Amazon fulfillment center, waiting to ship the moment a Buy Box order lands. The rest sits in your own warehouse, because you're fulfilling merchant orders yourself, running a Shopify store on the side, or holding back stock for wholesale.
Amazon shows you one version of your inventory. Your production system shows you another. Most small manufacturers reconcile the two the same way: a spreadsheet, updated by hand, usually a few units off by the time it's finished.
The problem isn't that FBA and FBM are complicated individually. It's that they're two separate inventory pictures that need to line up with a third: what your bill of materials says you can actually produce next. A generic Amazon repricer or inventory app tracks a stock number. It doesn't know that number is tied to a BOM, a lot of raw material, and a production run that hasn't happened yet.
Why this gets harder as you scale past one channel
A single-channel Amazon seller can get away with checking Seller Central once a day. A manufacturer running FBA, FBM, and a Shopify or wholesale channel on the same finished goods can't, because every channel is drawing from the same physical inventory without knowing it.
The failure mode is familiar: an FBM order comes in for units you've already committed to a wholesale customer, or a spreadsheet says you have more finished goods than you actually do because nobody updated it after this morning's production run. Neither system is wrong on its own. They're just not talking to each other, and reconciling them manually doesn't scale past a handful of SKUs.
What Nstock's Amazon integration actually does
Nstock connects to Amazon Seller Central through Amazon's Selling Partner API (SP-API), using Login with Amazon — the same kind of "sign in with..." authorization flow used by many apps. There are no API keys to generate or paste; you sign in to Seller Central and approve access.
Once connected, two things are available, both off by default until you turn them on from the Amazon Integration settings page:
- FBM orders sync as Nstock orders, with optional inventory deduction. Merchant-fulfilled Amazon orders flow into Nstock the same way a Shopify or WooCommerce order does. Turn on "Deduct inventory for Fulfilled by Merchant (FBM) orders" and fulfillment deducts the finished goods it contains from inventory automatically, just like those other channels.
- FBA orders import for reporting, if you turn it on. Turning on "Import Fulfilled by Amazon (FBA) orders for reporting" brings Amazon-fulfilled orders into Nstock for sales and COGS visibility, so you can see true cross-channel margin in one place. Nstock never deducts its own inventory for FBA orders — that stock already left your warehouse the moment you shipped it into Amazon's fulfillment network, so there's nothing left for Nstock to deduct.
- Costing follows the order, not the channel. Every imported Amazon order, FBA or FBM, carries the same FIFO/BOM-based cost calculation Nstock already applies to Shopify and WooCommerce orders, so COGS reporting doesn't need a separate spreadsheet per sales channel.
- Sync runs on demand. There's no scheduled or automatic sync yet. A "Sync Orders Now" button on the Amazon Integration settings page pulls in your most recent orders whenever you run it, so you stay in control of when new orders come in.
Where this fits if you're also selling on Shopify
A lot of manufacturers running Amazon as a channel are also running a DTC storefront — see multi-channel manufacturers on Shopify for how that side syncs. The two integrations are built on the same underlying pattern: orders flow in, fulfillment can deduct finished goods, and cost follows the BOM. If you're running both channels, the value compounds — one costing engine across every place you sell. For a closer look at how Amazon sellers and Shopify DTC brands overlap, see the Shopify DTC industry page.
FBA vs. FBM, and why the distinction matters for costing
It's worth being precise about the terms, because the accounting treatment differs. FBA (Fulfillment by Amazon) means Amazon holds your inventory and ships orders on your behalf — you pay Amazon fulfillment fees, and the units ship from a warehouse you don't directly control. FBM (Fulfillment by Merchant) means you or your 3PL ship the order yourself, so the inventory deduction happens in your own system the moment you fulfill it.
For a manufacturer, that distinction changes what "in stock" means depending on which report you're reading. FBA stock is committed the moment it leaves for Amazon's warehouse — it's no longer available for wholesale or FBM orders, even though you still legally own it and it still counts toward your COGS. That's exactly why Nstock draws a hard line between the two: FBM orders can deduct your Nstock inventory because that stock is still physically yours to ship, while FBA orders only ever inform reporting, never inventory, because the deduction already happened when you shipped that stock to Amazon in the first place. Getting that distinction right — rather than deducting the same units twice, or not accounting for them at all — is what keeps your on-hand counts and COGS accurate across both fulfillment models.
What this doesn't replace
This integration is not a replacement for Amazon's own Seller Central tools — repricing, advertising, Buy Box strategy, and account health stay in Seller Central, where they belong. What Nstock adds is the layer Amazon doesn't provide: tying every Amazon order back to the bill of materials and raw-material cost behind it, so the same inventory and costing engine that runs your production also runs your Amazon reporting.
Rollout notes
Nstock's Amazon app is still going through Amazon's own application review process, similar in scope to the review Nstock went through for its QuickBooks integration. Until that review completes, connections use Amazon's self-authorization mode, which currently only works for the seller account tied to the app in Amazon's Developer Console — it isn't yet available for every customer to connect themselves. If you're interested in connecting your own Amazon seller account, check with your Nstock contact on current availability before starting.
Frequently Asked Questions
Does Nstock support both FBA and FBM orders?
Yes. FBM orders sync as Nstock orders and can deduct inventory the same way a Shopify or WooCommerce order does, once you turn that setting on. FBA orders import for sales and COGS reporting if you turn on that separate setting, but Nstock never deducts its own inventory for FBA orders — that stock already left your warehouse when it shipped to Amazon.
Will connecting Amazon double-count my inventory?
No. FBM orders only deduct stock you still physically hold, and FBA orders never touch your Nstock inventory count at all — they're imported for reporting purposes only. Because the two order types are handled differently by design, on-hand counts and COGS stay accurate instead of double-counting units that already shipped to an Amazon fulfillment center.
How does this affect my COGS reporting?
Every Amazon order — FBA or FBM — carries the real FIFO/BOM-based cost of what shipped, the same costing engine used for Shopify and WooCommerce orders, so your margin numbers reflect actual production cost instead of a flat estimate per channel.
Can I disconnect or revoke access later?
Yes. Disconnect the integration from Nstock's Amazon Integration page at any time. Amazon doesn't provide a remote revocation endpoint for this kind of connection, so for full revocation on Amazon's side, also remove Nstock's access from Seller Central's "Manage Your Apps" page.