Amazon Inventory Management: How to Prevent Stockouts and Storage Fees

Amazon inventory management means keeping the right amount of stock in the right place so you never run out and never pay to store product that is not selling. In practice it comes down to four habits: forecast from real sales velocity, reorder on total lead time, feed FBA from a 3PL within Amazon's capacity limits, and clear slow stock before aged inventory fees hit.

Why is inventory management the top priority on Amazon?

You can have the best listing on Amazon, beautiful photography and a well tuned PPC account. None of it matters if you are out of stock. Drew Morgans, our founder, says that if there were ten commandments of selling on Amazon, the first three would be inventory, inventory, inventory.

Brands face two opposite risks, and both come from the same root cause, weak forecasting.

	Stockout	Overstock
What happens	Listing goes inactive, Best Sellers Rank falls, ads stop, competitors take your placements	Monthly storage fees, then aged inventory surcharges, lower IPI score, tighter capacity limits
Hidden cost	Weeks or months of extra ad spend to rebuild rank; slower review velocity	Cash tied up in product that could fund launches, ads or payroll
Recovery	Slow, and never guaranteed	Faster: discount, promote, liquidate or remove

When in doubt, lean toward a little too much rather than too little. A worked example: a product selling 50 units a day at $30 profit per unit loses $21,000 of profit in a two week stockout, before counting wasted ad spend and the months of lower rank that follow. Holding 1,000 extra units for three months costs a small fraction of that. Storage fees are recoverable. Lost rank often is not.

What makes Amazon inventory harder than it looks?

Capacity limits and IPI

Amazon caps how much each seller can send to FBA (Fulfillment by Amazon) through capacity limits. Your IPI (Inventory Performance Index), a score from 0 to 1,000, reflects how well you manage stock and influences the room you get. It weighs sell through, excess inventory, stranded inventory (stock at Amazon attached to an inactive listing) and in stock rate. We aim for 500 and treat 450 as the floor; below that, Amazon can restrict storage. Our guide to FBA capacity limits covers planning around them.

Storage and aged inventory fees

Amazon charges monthly storage by cubic foot, with much higher rates from October through December. On top of that, an aged inventory surcharge applies to units that have sat in fulfillment centers for more than about six months, and it climbs the longer they sit. Amazon changes these rates regularly, so pull the current fee schedule from Seller Central when you model costs. The pattern does not change: slow stock at Amazon gets more expensive every month, and most expensive in Q4.

Seasonality

Sunscreen spikes in May, space heaters in November, planners in December. If you stock evenly across the year you will run out at peak and overpay for storage in the slow months.

Lead times

For overseas manufacturing, a typical chain is 30 to 45 days of production, 30 to 45 days of ocean freight and 7 to 14 days for customs and FBA check in. That is 90 to 120 days before new stock is sellable. Miss the window and your options are expensive air freight or a stockout.

Cash flow

Inventory ties up cash. A brand doing $100,000 a month in revenue with 60 day turns has roughly two months of product sitting in the system at any time. Many brands under order because they cannot fund large buys, then stock out. Inventory planning is a finance decision as much as an operations one.

How do you calculate reorder points for Amazon?

Here is the system we use for the brands we manage.

1. Calculate true sales velocity. Units sold in the last 90 days divided by 90 gives daily velocity. Adjust it: multiply for peak season, add expected lift for planned deals, and use the last 30 days instead of 90 if sales are clearly accelerating. Amazon's restock recommendation is a useful starting point, but it does not know your production lead time or your promo calendar.
2. Add up total lead time. Production plus freight plus customs plus FBA check in plus a safety buffer. Example: 35 + 40 + 14 + 21 days of buffer = 110 days.
3. Set the reorder point. Daily velocity times total lead time. At 20 units a day and 110 days, reorder when you are down to about 2,200 units available and inbound.
4. Size the order. Cover the lead time plus 30 to 60 days of overage for demand spikes and supplier or receiving delays. Avoid more than about 90 days of overage outside peak season, because that stock is better stored somewhere cheaper than FBA.
5. Track sell through. Sell through rate is units sold and shipped over 90 days divided by the average units in FBA over the same period. Find it per product in the FBA Inventory tool and overall under Inventory Performance.

Use a system, not a spreadsheet someone updates when they remember. Whatever tool you choose should sync with every sales channel, forecast demand, alert you when stock runs low and track inbound shipments. We run our own analytics and alerting internally so days of cover is visible for every product, every day.

Should you send all your inventory to FBA or use a 3PL?

For most growing brands, not all of it. FBA is excellent at fast Prime shipping, customer service and returns. It is not built for holding months of stock, shipping wholesale or DTC orders, or flexing when capacity limits tighten.

Need	FBA	3PL warehouse
Prime badge and fast delivery on Amazon	Yes	Only by feeding FBA or through Seller Fulfilled Prime
Holding 3 to 6 months of bulk stock	Expensive, and limited by capacity	Yes, usually at lower cost
Shopify, wholesale and TikTok Shop orders	Possible through Multi Channel Fulfillment, with limits	Yes, from one inventory pool
Kitting, bundles, inserts, relabeling	Limited	Yes
Inspecting returns before they go back on sale	Limited control	Yes

Our model: FBA holds 60 to 90 days of inventory, and our own 3PL warehouse in Kansas City holds the rest. We receive container loads from manufacturers, inspect and prep them, and send FBA shipments in waves that fit within capacity limits. The same stock ships Shopify, wholesale and TikTok Shop orders. We set it up because we wanted control: to prep for Amazon, add inserts, build kits and variety packs, and move fast without depending on anyone else's warehouse.

Always keep a fulfillment backup

In 2020, Amazon restricted FBA inbound shipments to essential goods. Brands that were 100% FBA had product stuck in warehouses with no way to sell it. The brands we had set up with FBM (Fulfilled by Merchant) listings and a 3PL kept selling, and many grew. Whether it is your own warehouse, a 3PL or a hybrid, you need to be able to flip a switch and fulfill orders yourself. For most products FBM is the emergency backup; for very large or heavy items where FBA fees break the unit economics, it can be the primary model. Decide per product. Our FBA vs FBM guide covers the tradeoffs.

What should you do when inventory is running low?

Slow demand to protect rank until stock lands. Our rule of thumb for advertising by days of cover:

Days of stock left	Advertising action
30 or more	Normal bids.
15 to 29	Cut bids about 25%, pause broad and auto campaigns, keep exact match only.
7 to 14	Cut bids about 50%, exact match only, halve budgets.
Under 7	Pause everything except brand defense.

A modest price increase can also stretch stock. When replenishment is in transit, restore bids gradually starting about a week before it is due to arrive. Never launch a Lightning Deal or big promotion on a product that cannot absorb the spike; going out of stock mid deal is worse than not running it. See how we tie ads to inventory in our Amazon PPC work.

How do you avoid aged inventory and long term storage fees?

Amazon flags excess inventory when a product has more than about 90 days of supply or units aging past 90 days. Watch days of supply by product and move in order:

1. At about 60 days of supply: test a 10% to 15% discount and watch it for two to four weeks.
2. At about 90 days: add a coupon, a promotion or a bundle with a faster selling product.
3. At 120 days or more: liquidate through Amazon's own liquidation programs or a third party buyer.
4. Remove it: create a removal order to a 3PL, where storage is cheaper and the stock can serve DTC orders or future restocks.
5. Dispose or donate: the last resort, with zero recovery.

Rationalize the catalog

Many catalogs carry a long tail of SKUs that produce little revenue but drag down IPI and rack up storage. For each slow SKU ask three questions: is it profitable after storage fees, does it sell steadily, and does it matter strategically as a bundle component, gateway product or range filler? If the answer is no to all three, liquidate or discontinue it and put that cash into your winners.

What are the most common Amazon inventory mistakes?

• Ordering to supplier MOQs instead of demand. A 5,000 unit minimum order quantity on a product selling 50 a day is 100 days of stock. Negotiate, split shipments or stage the excess in a 3PL.
• Checking capacity limits after production. Check them before you place the order and plan shipments in waves.
• Sending everything to FBA. You pay premium storage for months of stock.
• Panic air freight. Reordering at 15 days of cover can wipe out months of profit on freight. Reorder at total lead time plus buffer.
• Ignoring promo impact. Before any deal, ask whether you can sustain the lift if it works.
• Missing hazmat flags. Check every product for dangerous goods status before creating a shipment; hazmat must ship separately and needs Amazon approval.
• Not watching stranded inventory. Stock sitting behind an inactive listing earns nothing and hurts IPI. Fix it right away.

How do Q4 and Prime Day change your inventory plan?

Peak events concentrate risk. Our Q4 pattern, which works the same way for Prime Day in July:

1. August to September: land Q4 inventory at the 3PL rather than FBA, where October storage rates would apply.
2. Late September: send the first wave to FBA, enough for October and November.
3. Early November: send the second wave for Black Friday, Cyber Monday and December.
4. January: pull unsold excess back out before it ages.

Full event plans are in our Black Friday and Q4 guide and our Prime Day playbook.

How should manufacturers and multi channel brands manage inventory?

Once a brand sells on Amazon, its own Shopify site, Walmart Marketplace, TikTok Shop and retail accounts, inventory becomes a different job. Many brands we talk to split sales roughly evenly between their own website and Amazon, and each channel has its own fulfillment rules.

• One view of stock. Track available inventory across every channel in real time so a spike on one does not oversell another.
• Several fulfillment methods at once. FBA, FBM, WFS (Walmart Fulfillment Services), a 3PL and direct to retail each need their own allocation.
• Retail and EDI. Wholesale accounts that order through EDI (electronic data interchange) need stock reserved and prepped to their standards.
• Vendor Central (1P) brands, where Amazon buys wholesale, do not control stock at Amazon directly. Forecast Amazon's purchase orders, keep fill rates high and keep a Seller Central (3P) or FBM path open for items Amazon under orders.
• Food, beverage and CPG. Watch expiration dating rules for FBA and manage lots so older stock ships first.
• Location. Stock held in the middle of the country reaches more customers faster and cheaper than stock on one coast. That is part of why we run our warehouse in Kansas City.
• Profit by channel. Know your fulfillment cost per order on each channel so you are not losing money on shipping or pricing yourself out.

Our multi marketplace team plans inventory across all of these as one pool.

Frequently Asked Questions

How do I prevent stockouts on Amazon?

Calculate daily sales velocity from the last 90 days, adjust it for seasonality and promotions, and reorder when stock on hand plus inbound falls to velocity times total lead time plus a safety buffer. Keep a 3PL or FBM backup, and cut ad spend as days of cover drop so you do not burn stock before replenishment arrives.

What is a good IPI score on Amazon?

IPI runs from 0 to 1,000. We aim for 500 and treat 450 as the floor, because scores below that can lead Amazon to restrict storage. Raise it by clearing excess and aged stock, fixing stranded listings and keeping best sellers in stock.

How can I avoid Amazon aged inventory fees?

Watch days of supply per product and act early: discount at around 60 days of supply, add promotions at 90, and liquidate or create a removal order beyond 120. Pulling slow stock back to a 3PL is usually far cheaper than letting it age in FBA.

How much inventory should I keep in FBA?

For most brands, about 60 to 90 days of supply in FBA, with the rest in a 3PL or AWD that feeds Amazon as capacity allows. Before peak seasons, send stock in waves so it arrives in time without paying Q4 storage rates for months.

When does a brand need a 3PL alongside FBA?

When capacity limits stop you sending what you need, when storage fees start eating margin, or when you sell on more than one channel. A 3PL lets you hold bulk stock cheaply, feed FBA in batches and ship Shopify, wholesale and marketplace orders from the same inventory.

What is a healthy inventory turnover for Amazon?

Many brands aim for roughly 6 to 12 turns a year, which means about 30 to 60 days of stock on hand, adjusted for lead time and seasonality. Longer lead times and seasonal peaks justify holding more, ideally outside FBA.