Amazon FBA Inventory Management: Restock Timing, Storage Fees, and Stock Limits

Amazon FBA inventory management is deceptively simple on the surface. You ship products to Amazon, they store and ship them for you, and customers get Prime delivery. The complexity is in the economics: FBA charges you for every cubic foot of space, penalizes slow-moving stock, and can restrict how much you send with little advance notice.

For sellers who treat FBA as a black box and ship inventory in bulk whenever they feel like restocking, costs spiral fast. Amazon’s 2025 FBA fee schedule shows that a single standard-size unit sitting at FBA for 12 months accumulates $4-8 in storage fees alone, on top of the fulfillment fees. Multiply that across hundreds of SKUs, and poor FBA inventory management quietly becomes your biggest margin leak.

This guide covers the FBA-specific challenges that matter most: storage fee tiers, restock limits, IPI scoring, aged inventory surcharges, and stranded inventory. For the broader multi-channel picture, start with the Amazon inventory management hub.

FBA storage fee structure

Amazon’s FBA storage fees are not flat. They vary by time of year, item size, and how long inventory has been sitting:

Monthly storage fees (2025-2026 rates)

Period	Standard-size (per cu ft)	Oversize (per cu ft)
January - September	$0.87	$0.56
October - December	$2.40	$1.40

The Q4 spike is significant. A pallet of standard-size products that costs $261 to store in August costs $720 in October. Sellers who send large FBA shipments in September to “prepare for the holidays” often do not realize they are paying nearly 3x the storage rate for weeks before sales volume picks up.

Aged inventory surcharge

On top of monthly storage, Amazon charges an aged inventory surcharge for units that have been at FBA for more than 181 days:

• 181-210 days: $0.50 per cu ft (on top of monthly storage)
• 211-240 days: $1.00 per cu ft
• 241-270 days: $1.50 per cu ft
• 271-300 days: $2.00 per cu ft
• 301-330 days: $2.50 per cu ft
• 331-365 days: $3.00 per cu ft
• 365+ days: $6.90 per cu ft or $0.15 per unit, whichever is greater

These surcharges are charged on the 15th of each month. A product that seemed profitable at 60-day sell-through becomes a money pit at 200 days. This is why accurate sell-through velocity data is critical for every SKU you send to FBA.

Inventory Performance Index (IPI)

Amazon uses the IPI score to measure how well you manage FBA inventory. The score ranges from 0 to 1,000, and it directly affects how much inventory you can store.

What affects your IPI score

Amazon has not published the exact formula, but based on Seller Central documentation and observed behavior, four factors drive the score:

• Excess inventory percentage: Units at FBA that are projected to cost more in fees than they will generate in profit. Keeping this under 10% is the baseline.
• Sell-through rate: Units sold and shipped over the past 90 days divided by average units on hand. Amazon wants to see consistent movement, not dormant stock.
• Stranded inventory percentage: Units at FBA not linked to an active listing. This should be 0% at all times.
• In-stock rate for replenishable ASINs: How often your top-selling products are available. Stockouts hurt this metric.

IPI thresholds and consequences

IPI score	Storage impact
600+	No limits; eligible for additional storage benefits
400-599	Standard storage limits apply
Below 400	Reduced storage limits; restock limits tighten significantly
Below 350	Severe restrictions; may be limited to weeks of cover only

Amazon evaluates IPI scores at the end of each quarter and applies storage limits for the following quarter. If your score drops below 400 in the evaluation period, you will enter the next quarter with restricted capacity, right when you might need it most.

A 2024 Marketplace Pulse analysis found that approximately 30% of active FBA sellers operate with IPI scores between 350 and 450, meaning they are either at or dangerously close to the threshold where storage restrictions bite.

Restock limits and capacity management

Amazon sets restock limits at the storage-type level (standard-size, oversize, apparel, footwear). These limits tell you the maximum number of units you can have at FBA including units currently in fulfillment centers plus units in transit to them.

How restock limits work

Your available capacity = Restock limit - (On-hand inventory + Inbound inventory + Inbound working + Inbound shipped)

If your restock limit for standard-size is 5,000 units and you have 3,200 on hand plus 800 inbound, your available capacity is 1,000 units. That is it. Amazon will reject inbound shipments that exceed your limit.

Strategies for tight restock limits

When capacity is limited, every unit you send must earn its spot:

• Prioritize by velocity and margin: Send your fastest-selling, highest-margin SKUs first. A SKU selling 10 units per day should get restocked before one selling 1 unit per day.
• Reduce days of cover: Instead of sending 90 days of stock, send 30-45 days and restock more frequently. This requires more shipments but frees capacity for more products.
• Remove aged inventory: Products sitting at FBA for 150+ days without strong sales velocity should be removed or liquidated before they consume capacity and incur surcharges.
• Time inbound shipments: Create shipments when existing inventory is 14-21 days from stockout, accounting for receiving delay. Sending too early wastes capacity; sending too late means stockouts.

Stranded inventory: the silent cost center

Stranded inventory consists of units at FBA that are not linked to an active listing. These units cost you storage fees with zero possibility of generating revenue. Common causes:

• Listing suppressed due to detail page issues (missing images, incomplete information)
• ASIN deleted or merged
• Listing closed due to pricing errors or policy violations
• Listing deactivated after returning from vacation mode
• Product matching errors after catalog changes

Amazon’s Stranded Inventory Report in Seller Central shows affected ASINs, but many sellers check it infrequently. A 2024 eComEngine survey found that the average FBA seller has 2-4% of their FBA inventory in stranded status at any given time. For a seller with 10,000 units at FBA, that is 200-400 units generating nothing but fees.

Check stranded inventory weekly. Set a calendar reminder. Fix the listing issue or create a removal order. Every week a stranded unit sits at FBA costs you $0.02-$0.05 per unit in storage alone, and that is before the aged inventory surcharge starts.

Restock timing for FBA

Getting restock timing right is the core skill of FBA inventory management. Send too early, and you waste capacity and pay storage fees on slow-moving stock. Send too late, and you stock out, lose ranking, and bleed PPC budget trying to recover.

The FBA restock timeline

A typical FBA restock involves these time blocks:

• Supplier lead time: 7-90 days depending on domestic vs. overseas sourcing
• Quality check and prep: 1-3 days
• Shipment creation and transit to FBA: 3-7 days for carrier delivery
• Amazon receiving and processing: 3-14 days (highly variable)

Total lead time from reorder to available-for-sale: 14-114 days depending on your supply chain.

The Amazon receiving window is the most unpredictable piece. During peak periods (August-November), receiving can take 2-3 weeks. During slow periods, it might take 3-5 days. Build your reorder point calculation on your worst-case receiving time from the past 6 months, not the average.

Reorder point formula for FBA

A reliable reorder point formula for FBA:

Reorder Point = (Average daily sales x Total lead time in days) + Safety stock

Where total lead time includes supplier lead time + prep time + transit to Amazon + Amazon receiving time.

Example: A SKU sells 8 units per day. Supplier lead time is 14 days, prep is 2 days, transit is 5 days, and Amazon receiving averages 10 days. Safety stock is 7 days of cover.

Reorder point = (8 x 31) + (8 x 7) = 248 + 56 = 304 units

When on-hand at FBA drops to 304 units, place the next order. For detailed formulas including seasonal adjustments and safety stock calculations, see how to prevent Amazon stockouts.

Multi-channel FBA sellers: allocation decisions

If you sell on Amazon plus other channels, you face an allocation question: how much inventory goes to FBA vs. stays in your warehouse?

There is no universal ratio. The right split depends on:

• Channel mix: If 70% of your revenue comes from Amazon, most stock should be at FBA. If it is 40%, you need more local inventory for other channels.
• Prime badge value per SKU: Some products see a significant conversion lift from Prime. Others sell fine without it. Measure the actual difference before defaulting to FBA for everything.
• Storage cost comparison: Compare FBA’s per-cubic-foot rates to your warehouse cost. For bulky or slow-moving items, your warehouse is often cheaper.
• Stockout risk tolerance: FBA stockouts are more damaging than website stockouts because of BSR and ranking impact. Weight your Amazon allocation slightly higher than raw sales percentages suggest.

Using Amazon FBA inventory software lets you set allocation rules per SKU and automatically adjust based on sell-through velocity across all channels, rather than guessing at a fixed split.

Common FBA inventory mistakes

• Sending 90+ days of supply to FBA when restock limits are tight (30-45 days is more capital-efficient)
• Ignoring the Q4 storage fee spike and shipping large quantities in September
• Not checking stranded inventory reports weekly (2-4% of FBA inventory is typically stranded)
• Using Amazon’s restock recommendations without adjusting for multi-channel sales
• Not accounting for Amazon receiving delays in reorder point calculations (the 3-14 day range matters)
• Keeping unprofitable SKUs at FBA because removal feels wasteful (the sunk cost trap)

Quick Reference

• FBA storage fees: $0.87/cu ft (Jan-Sep), $2.40/cu ft (Oct-Dec) standard-size
• Aged inventory surcharge starts at 181 days ($0.50/cu ft), maxes at 365+ days ($6.90/cu ft)
• IPI score threshold: 400 minimum to avoid storage restrictions; target 600+
• Approximately 30% of FBA sellers operate near the 400 IPI threshold (Marketplace Pulse 2024)
• Amazon receiving takes 3-14 days; plan for worst case during peak
• Average FBA seller has 2-4% stranded inventory at any given time (eComEngine 2024)
• Reorder point = (daily sales x total lead time) + safety stock
• Send 30-45 days of cover instead of 90+ when capacity is limited
• Check stranded inventory weekly; every stranded week costs $0.02-$0.05/unit minimum

FBA Metric	Baseline floor	Strong target
IPI score	400	600+
Stranded inventory	Under 3%	0%
Aged inventory (181+ days)	Under 15%	Under 5%
In-stock rate (top ASINs)	93%	97%+
Days of cover at FBA	60 days	30-45 days