Automated inventory replenishment across FBA, AWD, 3PLs and your own warehouse

Replenishment sits behind every stockout and every pallet of dead stock: when to reorder, how much, and where the units go. With one warehouse a spreadsheet can carry it. With FBA, AWD, a 3PL and your own building, it becomes a routing problem with lead times measured in months.

Why does replenishment break once stock sits in more than one place?

An FBA offer sells from stock Amazon can ship. Units at a 3PL or on your own racks are upstream supply that still has to move. A plan built on total units looks healthy until the listing goes out of stock while the 3PL holds two months of cover.

Three things usually go wrong at once:

• Lead time is treated as one number. It really stacks production, freight, receiving at the 3PL or AWD, prep and labeling, and the inbound leg into FBA. Miss a leg and every reorder point is too low. Prep is now always your leg in the US: Amazon stopped offering FBA prep and item label services on January 1, 2026, so units must be prepped and labeled before they ship (checked October 23, 2026).
• Nobody owns the split. One person plans supplier POs, another plans FBA shipments.
• Capacity shows up last. FBA sets limits in cubic feet per storage type, so a plan written in units can be impossible to ship.

How do you calculate a reorder point and reorder quantity?

The reorder point is safety stock plus forecast demand during the lead time, as Oracle's reorder point planning documentation defines it (checked October 4, 2026). Ecommerce changes what goes into each term.

Example: a SKU sells 40 units a day across channels. Production and ocean freight take 60 days and the 3PL-to-FBA leg adds 15, so lead time is 75 days and lead-time demand is 3,000 units. Add 600 units of safety stock and the reorder point is 3,600, measured against stock in every location plus open orders.

When the position crosses that line, order the gap between your target cover and the current position, rounded up to the supplier's case pack and minimum order.

Safety stock should scale with forecast error and lead-time swings, not a flat two weeks for every SKU. See safety stock and days of cover.

What does each node do in a multi-node plan?

Units waiting in AWD sit outside FBA fulfillment centers, so they are not part of FBA capacity usage, and AWD has its own capacity allocation. Amazon also names staying outside FBA storage limits as a benefit of AWD auto-replenishment, and AWD's price already covers FBA inbound placement (checked October 4, 2026). Auto-replenishment runs on Amazon's recommended quantity, a minimum and maximum you set, or not at all. With auto-replenishment on, Amazon treats a product as in stock and buyable once AWD receives it, so for that SKU the supplier lead time can end at AWD. Where several seller SKUs share one ASIN, Amazon applies the highest minimum and maximum set across those SKUs, so one stale setting can overfill FBA. Amazon says AWD distributes to non-Amazon channels too; if the same pool feeds Walmart Fulfillment Services or your own store, someone still decides each channel's share. For China-sourced stock, Amazon also offers Global Warehousing and Distribution (GWD) in Shenzhen, Shanghai and Ningbo, which it says costs up to 45% less for storage than US AWD and refills FBA across the border (checked November 7, 2026).

How do FBA capacity limits change the plan?

Amazon sets one FBA capacity limit per storage type each month, in cubic feet, and capacity cannot be exchanged between storage types such as standard-size and oversize. Usage counts stock already in fulfillment centers plus every shipment you have created that has not arrived, as Amazon's capacity announcement explains (checked October 4, 2026). The Capacity Monitor shows usage and estimated limits for the next three months, and the capacity limits page says limits are typically announced in the fourth week of the month, confirming the next month and re-estimating the two after it (checked October 23, 2026). New professional accounts active in FBA for under 39 weeks get no limits; individual accounts are fixed at 15 cubic feet. Capacity Manager lets you request extra space at a reservation fee you set: Amazon reviews requests typically twice a week, grants the highest fee per cubic foot first, and pays a $0.15 performance credit per dollar of FBA sales, prorated by the share of your limit the extra space represents (break-even sales here). If on-hand stock plus open shipments would pass the limit, Amazon blocks new shipments. See FBA capacity limits.

So the monthly announcement is a planning date: re-run next month's FBA shipments against the confirmed cubic feet the day it lands, and move what does not fit to AWD, a 3PL or the month after.

Can AWD still hold all your buffer stock?

Check before you plan on it. Amazon's AWD capacity page gives AWD its own cap: base capacity splits into palletizable and standard facilities from November 9, 2026, and from January 7, 2027 a shipment that would pass your allocation cannot be created (read November 7, 2026). The allocation comes from your past AWD usage, so a plan that moves more of the buffer into AWD next year can be the one that does not fit.

For the plan, that adds three steps:

• Convert the AWD share of the buffer to cubic feet, on hand plus open shipments, by facility type, and compare it with Capacity Manager.
• If it is short, ask by December 4, 2026. Amazon takes base-allocation requests by email from November 9 and wants a six-month shipment plan by SKU and facility type.
• Route the overflow. Anything still over goes to a 3PL or a storage reservation, which bills on reserved volume from February 1, 2027, used or not.

The dates and costs are in FBA capacity limits, and our AWD capacity guide has the worksheet and the December 4 email checklist.

Separately from capacity, Amazon can block new shipments for a single product. The next section lists why.

Why is Amazon blocking FBA shipments for one SKU, and what should the plan do?

Amazon's page on product-level shipment restrictions lists the reasons it may stop you creating shipments for a product (checked November 7, 2026). Each one needs a different response in the replenishment plan, because a blocked SKU's next FBA shipment will not happen on the date the plan assumed.

The two pages do not match yet: the restriction page describes stranded stock as having no active offer, while the stranded page adds search suppression and says a shipment with a stranded ASIN will not be processed. Until Amazon says otherwise, treat a suppressed SKU as a possible block.

The block covers transfers from AWD too: if FBA already holds too much of a product, AWD cannot send more, and Amazon says it adjusted auto-replenishment to match. A plan that keeps scheduling those transfers will show stock arriving that never does.

So plan in cubic feet per storage type, not units, because bulky SKUs eat capacity fast. When space is tight, rank SKUs by days of cover and margin and ship the ones closest to running out first, then schedule the next FBA shipment against next month's estimated limit.

There is a floor as well as a ceiling. In the US, eligible products pay a low-inventory-level fee when both the 30-day and 90-day historical days of supply are below 28 days, calculated per FNSKU since January 15, 2026. One exemption covers SKUs where 70% or more of the inventory was auto-replenished through AWD over the prior 90 days, so a SKU that also takes regular 3PL shipments can lose it. A buffer held at a 3PL has to keep FBA above that line on its own schedule. Overfilling FBA to dodge a stockout moves the problem into long-term storage fees. Amazon changes this test on February 1, 2027; see what changes in the fee.

How does Growth OS compute reorder quantities and draft POs and shipments?

Growth OS is deployed on your own accounts, so replenishment runs on your data and that data stays yours. You keep your accounts, your data and the custom code we build; the Growth OS base is licensed to you. It tracks demand and days of cover per SKU and channel, and adds channel demand together to size the supplier order. Each lead-time leg is refreshed from actual receipts, so a supplier slipping from 45 to 55 days moves the reorder point without anyone editing a sheet.

Amazon's restock recommendations, available as an SP-API Restock Inventory report, are one input. The FBA Restock tool behind them takes supplier lead time, your lead time, replenishment frequency, case pack and minimum quantity (checked October 4, 2026). They plan shipments into Amazon only, so a SKU where they disagree sharply with the plan gets flagged for review. The same inventory position feeds inventory-aware ad spend, so ads ease off SKUs about to run out.

On top of the base we build what your operation needs, such as the inventory and replenishment agent, which can read supplier emails and update PO dates. We have built this plumbing before: Seller7, a multi-marketplace seller OS we built.

Where is your replenishment leaking?

To check one SKU first, the reorder point calculator adds every lead-time leg and safety stock. For your whole account, start with the free 24-hour diagnostic in the Ops Gap Diagnostic: connect Amazon with Login with Amazon, no password shared, and get a report of what is going wrong within 24 hours of connecting, on business days. We only read data; we never change listings, prices, stock or ads. Rather not connect? The free Quick Scan works from uploaded reports, and the paid Deep Diagnostic covers every channel. If you already know this is the gap, see how Growth OS runs replenishment alongside listings, orders, advertising and reporting.

If reorder points and purchase orders are still worked out in a spreadsheet, a workflow automation project can turn that routine into low-stock alerts and draft POs your team approves. The low-stock alerts and draft purchase orders recipe shows the steps, and the FBA inbound shipment from an approved PO recipe picks up once a PO is approved, building the inbound plan while a person chooses placement and freight. In between, the supplier PO acknowledgement and ETA tracking recipe keeps open-PO dates current as suppliers confirm and ship dates slip, so the reorder point counts units on the right day.