Quick answer: The costliest FBA inventory mistakes are holding too much stock, letting it age, leaving it stranded without an active listing, and running out of your best sellers. Amazon measures all four in your Inventory Performance Index (IPI), and your IPI score influences your FBA capacity limits. Amazon suggests keeping enough inventory to cover 30 to 60 days of expected sales, treats more than 90 days of supply as excess, and charges an aged inventory surcharge on units stored 181 days or longer.
Inventory problems rarely trigger a suspension directly, but they drain cash through fees, shrink the space Amazon gives you, and create the stock-outs and listing errors that hurt your account. This guide covers the mistakes Amazon’s own inventory tools are built to catch.
How Amazon Measures Your Inventory
Amazon’s Inventory Performance dashboard scores four areas, each shown as Excellent, Good, Fair, or Poor:
| Area | Amazon’s measure | The mistake it catches |
|---|---|---|
| Excess inventory | Percentage of FBA units with more than 90 days of supply | Ordering more than demand supports |
| Sell-through | Units shipped in 90 days divided by average units on hand | Slow-moving stock tying up space |
| Stranded inventory | Percentage of FBA units not available for purchase | Listing problems left unfixed |
| In-stock rate | Time replenishable ASINs were in stock over 30 days, weighted by sales | Running out of best sellers |
The IPI score and dashboard are available to sellers on the Professional selling plan. Newly created ASINs do not affect the IPI score in their first 90 days.
Mistake: Sending More Than You Can Sell
Amazon considers an item excess when it has over 90 days of supply based on forecasted demand. Excess inventory raises storage costs and lowers your IPI. Amazon’s dashboard shows an estimated total storage cost, which projects the monthly storage fees and aged inventory surcharges you would pay over three years if you took no action.
Amazon’s guideline is to keep enough stock for 30 to 60 days of expected sales. For overstock, Amazon points to price reductions, Amazon Outlet deals, Multi-Channel Fulfillment through your other sales channels, and removal orders.
Mistake: Letting Inventory Age
Amazon charges an aged inventory surcharge (previously called the long-term storage fee) on units stored 181 days or longer, assessed on the 15th of each month on top of monthly storage fees. Amazon calculates age on a first-in, first-out basis across its whole network, so the oldest units are counted as sold first regardless of which unit actually shipped.
Under the rates Amazon lists from January 16, 2026, the surcharge starts at $0.50 per cubic foot for items aged 181 to 210 days (excluding certain apparel, shoe, bag, jewelry, and watch items), rises to $5.45 per cubic foot from 271 days, and reaches the greater of $7.90 per cubic foot or $0.35 per unit for items aged 456 days or more. Rates change, so confirm current figures on Amazon’s fee page before planning.
Amazon recommends removing inventory before it reaches 365 days and lets you set up automated removals for aged stock.
Mistake: Ignoring Stranded Inventory
Stranded inventory is sellable product in a fulfillment center with no active listing, so it cannot be bought but still incurs fees. Amazon lists it as one of the four IPI factors. Check the Fix stranded inventory page regularly; common causes are listing errors, suppressed listings, and closed offers.
Mistake: Running Out of Best Sellers
Amazon’s in-stock rate tracks how often your replenishable ASINs were available, and the dashboard estimates FBA lost sales for out-of-stock days. Amazon’s Restock today button flags SKUs whose days of supply are shorter than your restock lead time. If a SKU is not meant to be replenished, you can hide its recommendation so it does not count against your in-stock rate.
Mistake: Not Planning Around Capacity Limits
Amazon sets FBA capacity limits for each storage type monthly, influenced by your IPI score, sales history, seasonality, forecasts, new selection, scheduled deals, fulfillment center capacity, and shipment lead time. Limits are typically announced in the fourth week of the month. Key points from Amazon’s page:
- Individual selling accounts have a fixed limit of 15 cubic feet.
- New Professional accounts active in FBA for less than 39 weeks do not receive capacity limits.
- Capacity Manager lets you request more space at a reservation fee you set, offset by a $0.15 performance credit per dollar of sales from that extra space. You pay any balance not offset.
Mistake: Shipping Inventory That Does Not Match the Rules
Inventory that breaks FBA product, packaging, or labeling requirements may be refused or disposed of at your expense and is not eligible for reimbursement. See our guide to the facts every FBA seller should know and Amazon’s barcode rules.
Our Amazon inventory reconciliation service reviews your FBA records for lost, damaged, and unreimbursed units. To keep the rest of your account in good shape, see our account health maintenance service.
Frequently Asked Questions
What is a good amount of FBA inventory to hold?
Amazon’s guideline is enough to cover 30 to 60 days of expected sales. Over 90 days of supply is treated as excess.
When does Amazon charge aged inventory fees?
The aged inventory surcharge applies to units stored 181 days or longer, assessed on the 15th of each month.
Does my IPI score affect how much I can send to Amazon?
Yes. Amazon says your capacity limit is influenced by your IPI score along with other factors such as sales forecasts and fulfillment center capacity.
What is stranded inventory?
Sellable units in a fulfillment center that have no active listing and therefore cannot be purchased.
Do removal orders improve my IPI?
Once a removal or liquidation is placed, those units are no longer considered in the IPI, though Amazon notes the score takes time to reflect it.
Get Your Inventory Reviewed
Submit your case for a free assessment, or book a consultation.
Sources
- Amazon Seller Central, Inventory performance
- Amazon Seller Central, IPI frequently asked questions
- Amazon Seller Central, FBA capacity limits
- Amazon Seller Central, Aged inventory surcharge
- Amazon Seller Central, Product packaging requirements
