Amazon Inventory Management: FBA Restock Limits, IPI Score & Automation

Amazon Inventory Management in 2026: What Has Changed

Amazon inventory management has never been static, but the changes since late 2025 have been some of the most consequential for sellers in years. If you are managing Amazon inventory with the same playbook you used in 2023, you are overpaying on fees, underutilizing your storage capacity, and leaving money on the table.

The biggest shifts in 2026 center around three areas: the fee structure, capacity limits, and the IPI thresholds that determine how much inventory you can actually store at Amazon fulfillment centers.

Fee Structure Changes

Amazon restructured FBA fees effective January 2026. The per-unit fulfillment fee for standard-size items increased by an average of $0.04 to $0.08 per unit, depending on weight tier. The more significant change is the low-inventory-level fee, which Amazon introduced in 2024 and expanded in 2026. This fee penalizes sellers who maintain less than 28 days of supply at fulfillment centers relative to their sales velocity. For a product selling 10 units per day, you need at least 280 units at FBA to avoid the surcharge. The fee ranges from $0.32 to $0.97 per unit shipped, depending on how far below the 28-day threshold your inventory falls.

This creates a paradox: Amazon charges you more for having too much inventory (aged inventory surcharges) and now also charges you for having too little. The sweet spot for most SKUs is 30 to 60 days of supply at FBA, enough to avoid the low-inventory-level fee without triggering long-term storage penalties.

Capacity Limits Replace Restock Limits

Amazon fully transitioned from weekly restock limits to monthly capacity limits in 2024, and the 2026 iteration of this system is more dynamic. Your monthly capacity is now recalculated every month based on your IPI score, historical sales volume, seasonal trends in your product category, and your shipment lead time performance. Amazon also introduced the Capacity Manager, where sellers can request additional capacity above their monthly allocation by bidding a reservation fee per cubic foot. If your actual sales during the period exceed the threshold, Amazon refunds a portion of the reservation fee.

IPI Threshold Updates

The IPI (Inventory Performance Index) thresholds were adjusted for 2026. The restriction threshold remains at 400, drop below it, and your storage capacity is capped. The practical thresholds for most sellers are:

• Below 400: Storage capacity restricted. You will receive significantly less space at FBA and may not be able to send in new shipments until existing inventory sells through.
• 400 to 549: Standard capacity. You get a reasonable allocation but no preferential treatment.
• 550 and above: Expanded capacity. Amazon grants additional storage space and you have more flexibility during peak periods.

For multi-channel sellers, these changes mean that amazon inventory management is no longer just about keeping products in stock. It is about precision, maintaining inventory levels within a narrow band that avoids fees on both ends while maximizing your capacity allocation.

Understanding the IPI Score

The IPI score is a number between 0 and 1,000 that Amazon uses to evaluate how efficiently you manage your FBA inventory. It is recalculated every week and directly determines your storage capacity. Understanding what drives this score is essential because it is the single biggest lever you have over your FBA storage limits.

The Four Factors Behind the IPI Score

Amazon does not publish the exact formula, but the score is built from four measurable components. Each one carries different weight, and improving any single factor can move your score significantly.

1. Excess Inventory Percentage

This measures how much of your FBA inventory Amazon considers overstocked. Amazon flags inventory as excess when it estimates more than 90 days of supply based on your current sell-through rate and forecasted demand. If 25% of your units are classified as excess, your IPI score takes a meaningful hit.

How to improve it: Run a weekly excess inventory report. For SKUs with more than 90 days of supply at FBA, either reduce the price to accelerate sell-through, run a Deals promotion, create a removal order, or use Amazon's liquidation program. Do not let excess inventory sit and accumulate, the longer it stays, the worse it gets for your score and the more you pay in storage fees.

2. Sell-Through Rate

Sell-through rate is calculated as units sold and shipped over the past 90 days divided by the average number of units in FBA during that same period. A higher sell-through rate tells Amazon you are sending inventory that actually sells, not just parking it at their warehouses. Amazon targets a sell-through rate above 3.0 for most categories, though the ideal number varies by product type.

How to improve it: Reduce inbound shipment quantities for slow-moving SKUs. Instead of sending 500 units of a product that sells 3 per day, send 150 units and replenish more frequently. This keeps your average FBA inventory lower while maintaining the same sales velocity, which mathematically increases your sell-through rate. For SKUs with persistently low sell-through, move them to FBM or remove them from FBA entirely.

3. Stranded Inventory Percentage

Stranded inventory is stock sitting in FBA that cannot be sold because the listing is inactive, suppressed, or has an error. Amazon monitors how quickly you fix stranded inventory and factors the percentage of stranded units into your IPI score. Even a small percentage of stranded inventory can drag your score down because Amazon interprets it as poor inventory management.

How to improve it: Check the Fix Stranded Inventory page in Seller Central at least three times per week. Set up automatic email alerts for listing deactivations. Most stranded inventory is caused by listing errors that are straightforward to fix once identified. The key is response speed, fixing a stranded listing within 24 hours has minimal IPI impact, but letting it sit for two weeks causes real damage.

4. In-Stock Rate

In-stock rate measures how often your replenishable FBA SKUs have available inventory. Amazon weights this toward your best-selling products, running out of stock on a top-10 SKU hurts more than a stockout on a long-tail item. The in-stock rate calculation only covers products Amazon considers replenishable (products you have shipped to FBA at least once in the past 90 days).

How to improve it: Set reorder points with adequate lead-time buffers for every FBA SKU. Factor in Amazon's receiving delays, which average 5 to 14 days for standard shipments and can spike to 21 or more days during peak season. For your top 20% of SKUs by revenue, maintain a minimum of 30 days of supply at FBA at all times. Use safety stock formulas calibrated to your actual demand variability and lead-time variability for each SKU.

FBA Restock Limits Explained

FBA restock limits, now called capacity limits, determine how much inventory you can store at Amazon fulfillment centers in a given period. Understanding how they work is critical for planning inbound shipments, especially if you sell across multiple channels and cannot afford to have FBA inventory constraints disrupting your overall supply chain.

How Monthly Capacity Limits Work

Amazon calculates your monthly capacity as a volume measurement in cubic feet. The allocation considers four inputs:

1. IPI score: Higher scores open more capacity. Sellers above 550 receive the most generous allocations.
2. Sales velocity: SKUs with strong sell-through history get more implicit capacity because Amazon expects them to move quickly.
3. Historical shipment performance: If you consistently send accurate, well-prepped shipments that Amazon receives without issues, your capacity allocation trends upward over time.
4. Seasonal adjustments: Amazon adjusts capacity allocations for seasonal trends. If your product category peaks in Q4, you may see increased capacity starting in October, but only if your IPI supports it.

Your capacity limit is shown in Seller Central under the FBA Dashboard. It is updated monthly and covers all product size tiers combined. You can view your current usage, remaining capacity, and estimated limits for the next three months.

Requesting Additional Capacity

If your allocated capacity is not sufficient, Amazon's Capacity Manager lets you request additional space. Here is how it works:

• You specify the additional cubic feet you need for the upcoming period.
• You bid a reservation fee per cubic foot. The maximum fee Amazon has charged is around $2.00 per cubic foot, but winning bids vary by period and demand.
• Amazon evaluates requests and grants additional capacity if available.
• If your actual sales during the period generate enough revenue relative to the reserved space, Amazon refunds a portion or all of the reservation fee as a performance credit.

The Capacity Manager is most valuable ahead of peak seasons when your standard allocation would not cover the inventory you need to stage. Bid strategically: calculate the revenue you expect from the additional inventory and ensure the reservation fee is a small fraction of that revenue. For most sellers, paying $0.50 to $1.00 per cubic foot is worthwhile if the inventory it enables generates $50 or more in revenue per cubic foot during the period.

Using FBM as Overflow

When FBA capacity limits prevent you from sending enough inventory, Fulfillment by Merchant becomes your overflow strategy. The approach is straightforward: maintain FBM listings as backups for your FBA SKUs, and activate them when FBA inventory runs low or when capacity limits prevent replenishment.

For multi-channel sellers, this is where having your own warehouse pays off. Inventory stored at your 3PL or warehouse can fulfill FBM Amazon orders, Shopify orders, eBay orders, and any other channel simultaneously. The key is keeping your inventory sync tight so that a sale on any channel immediately decrements the shared pool and prevents overselling.

The FBA vs FBM Decision

Choosing between FBA and FBM is not a one-time decision. It is a per-SKU, per-season evaluation that multi-channel sellers should revisit quarterly. The following comparison lays out the key differences across the dimensions that matter most.

Factor	FBA (Fulfillment by Amazon)	FBM (Fulfillment by Merchant)
Cost per Unit	Fulfillment fee ($3.22 to $6.90+ for standard-size) plus monthly storage ($0.78 to $2.40/cu ft). Low-inventory-level fee if below 28 days supply.	Your warehouse labor + packing materials + outbound shipping. Typically $4.00 to $8.00 per order for standard items depending on carrier rates.
Delivery Speed	Prime 1-2 day delivery. Amazon handles shipping and last-mile.	3-7 business days standard. Seller Fulfilled Prime available but requires strict performance metrics.
Buy Box Weight	Strong advantage. FBA offers are preferred in the Buy Box algorithm, especially for Prime-eligible listings.	Disadvantaged unless enrolled in Seller Fulfilled Prime. FBM sellers need lower prices or exceptional metrics to compete.
Effort Required	Low ongoing effort. Amazon handles pick, pack, ship, customer service, and returns for FBA orders.	High ongoing effort. You manage warehouse operations, carrier relationships, customer service, and returns processing.
Best For	High-velocity, small-to-medium items with healthy margins. Products where Prime eligibility drives conversion.	Oversized or heavy items, slow movers, low-margin products, multi-channel SKUs that need warehouse flexibility.

When to Use FBA

Use FBA for products that meet three criteria: they sell fast enough that monthly storage fees stay low relative to revenue, they are small or standard-size so fulfillment fees are competitive, and they are on listings where Prime eligibility meaningfully impacts conversion rate. For most Amazon-first sellers, this covers their top 50 to 70% of SKUs by revenue.

When to Use FBM

Use FBM when the product is oversized or heavy (FBA dimensional weight fees make it uneconomical), when the product turns slowly (storage fees accumulate and aged inventory surcharges become a risk), when you sell the same product across multiple channels and need warehouse flexibility to allocate inventory dynamically, or when you have a strong fulfillment operation that can match or approach FBA delivery speeds. Many multi-channel sellers use a hybrid FBA/FBM strategy that assigns each SKU to the fulfillment method where it performs best on unit economics.

Stranded Inventory: Causes, Fixes, and Prevention

Stranded inventory is one of the most damaging and overlooked problems in amazon inventory management. It refers to inventory physically stored at Amazon fulfillment centers that cannot be purchased by customers because the associated listing is inactive, suppressed, or missing. You are paying storage fees on this inventory while generating zero revenue from it, and it drags your IPI score down every day it remains stranded.

What Causes Stranded Inventory

• Listing errors: A required product attribute is missing or incorrect, causing Amazon to suppress the listing. This is the most common cause and often results from bulk upload mistakes or Amazon changing attribute requirements for a category.
• Suppressed ASINs: Amazon suppresses listings that violate policy, have incomplete product detail pages, or trigger automated quality checks. Common triggers include missing main images, restricted keywords in the title, or pricing that falls outside Amazon's fair pricing guidelines.
• Condition changes: If you list a product as New but Amazon's system flags it as a condition mismatch (for example, product complaints about packaging), the listing can be deactivated while inventory remains at FBA.
• Expired listings: For products with expiration dates, Amazon automatically strands inventory that approaches or passes its expiration window.
• Deleted listings: If a listing is deleted accidentally or by a third party (a brand owner filing a complaint, or a catalog merge), the FBA inventory attached to that ASIN becomes stranded.

How to Fix Stranded Inventory

Go to Seller Central and navigate to Inventory > Fix Stranded Inventory. This page shows every stranded SKU with the reason it is stranded and a suggested action. Most fixes fall into one of these categories:

• Relist the product: If the listing was deactivated due to an error, fix the listing issue and reactivate it. The inventory automatically becomes sellable once the listing is active again.
• Update the listing: If a required attribute is missing or Amazon has changed category requirements, update the product detail page to comply.
• Create a removal order: If the inventory cannot be relisted (expired products, policy violations that cannot be resolved), create a removal order to have Amazon ship the inventory back to you or dispose of it.
• Match to an existing ASIN: If the listing was deleted but the product matches another active ASIN, you can match your inventory to the correct ASIN.

Prevention Through Automation

Set up automatic stranded inventory settings in Seller Central. Amazon can automatically attempt to relist stranded inventory when the listing is fixable. Enable automatic removal for inventory that has been stranded beyond a set number of days, 30 days is a reasonable threshold. This prevents stranded units from silently accumulating storage fees for months.

For sellers managing hundreds or thousands of SKUs, manual stranded inventory checks do not scale. Use the Stranded Inventory Report via the SP-API to pull stranded inventory data programmatically and build automated workflows that flag new stranded SKUs, attempt a fix based on the reason code, and escalate to a human only when automated resolution fails.

Long-Term Storage Fees and Aged Inventory Surcharges

Amazon charges escalating fees for inventory that sits at fulfillment centers too long. Understanding the fee schedule and having a strategy for managing aged inventory is essential for protecting your margins.

Monthly Storage Rates by Time Period

Standard storage fees are charged monthly and vary by time of year and product size:

• Standard-size, January to September: $0.78 per cubic foot per month.
• Standard-size, October to December: $2.40 per cubic foot per month (3x the off-peak rate, reflecting holiday warehouse demand).
• Oversize, January to September: $0.56 per cubic foot per month.
• Oversize, October to December: $1.40 per cubic foot per month.

Aged Inventory Surcharge

On top of monthly storage, Amazon applies an aged inventory surcharge for units that have been at FBA for more than 180 days. The surcharge schedule for 2026 is:

• 181 to 210 days: $1.50 per cubic foot surcharge.
• 211 to 240 days: $3.00 per cubic foot surcharge.
• 241 to 270 days: $4.50 per cubic foot surcharge.
• 271 to 300 days: $5.45 per cubic foot surcharge.
• 301 to 330 days: $5.45 per cubic foot surcharge.
• 331 to 365 days: $6.90 per cubic foot surcharge.
• 365+ days: $6.90 per cubic foot or $0.15 per unit, whichever is greater.

These surcharges compound quickly. A standard-size product occupying 0.5 cubic feet that has been at FBA for 270 days costs about $2.73 per unit just in surcharges, on top of the regular monthly storage fee. For a product with a $15 selling price and a 30% margin, that surcharge wipes out more than half of your profit per unit.

Removal Order Strategy

When inventory approaches the 180-day mark and shows no signs of selling through in time, you have four options:

1. Liquidate through Amazon: Amazon's FBA Liquidations program sells your excess inventory to liquidation partners. You typically recover 5 to 10% of the retail price. This makes sense when the alternative is paying surcharges that exceed the liquidation recovery.
2. Create a removal order: Have Amazon ship the inventory back to you. The removal fee is $1.04 per standard-size unit and $3.12 or more per oversize unit. Once returned, you can sell the inventory through other channels, bundle it, or store it at your own warehouse where carrying costs are lower.
3. Destroy the inventory: Amazon charges $0.32 per standard-size unit for disposal. This is the last resort for products with no residual value and no other channel opportunity.
4. Aggressive discounting: Before the 180-day mark, run a Lightning Deal, coupon, or price reduction to move the inventory. Even selling at break-even is better than paying surcharges.

When to Liquidate vs Remove

The decision depends on whether the inventory has value outside Amazon. If you sell on other channels and the product is still marketable, create a removal order and reallocate the inventory to Shopify, eBay, or wholesale. If the product is Amazon-specific (category restricted elsewhere, branded packaging, etc.) and you cannot discount it enough to move it, liquidation or disposal is the economically rational choice. Run the math: compare the total surcharges you will pay if the inventory stays versus the removal or liquidation cost. The answer is almost always that acting early is cheaper than waiting.

Multi-Channel Fulfillment (MCF)

Amazon's Multi-Channel Fulfillment program lets you use your FBA inventory to fulfill orders from non-Amazon sales channels. Shopify, your own website, eBay, or anywhere else. On paper, this sounds like a strong consolidation strategy. In practice, it comes with trade-offs that multi-channel sellers need to evaluate carefully.

How MCF Works

When a customer places an order on your Shopify store, you submit a fulfillment request to Amazon via the SP-API or through an integration app. Amazon picks, packs, and ships the order from your FBA inventory, just as it would for an Amazon order. The customer receives the package in Amazon-branded (or unbranded) packaging with no indication that Amazon fulfilled it.

Pros of MCF

• Fast shipping: MCF orders benefit from Amazon's fulfillment network. Standard MCF delivery is 3 to 5 business days, with expedited options for 2-day delivery.
• Consolidated inventory: You store inventory in one place (FBA) and fulfill all channels from that pool. This simplifies replenishment planning and reduces the total inventory you need to carry.
• Scalability: Amazon handles the fulfillment labor. You can scale order volume without adding warehouse staff or space.
• Reliable fulfillment: Amazon's fulfillment operation is consistently accurate and fast. For sellers without a strong in-house fulfillment operation, MCF provides enterprise-grade reliability.

Cons of MCF

• Higher fees: MCF fulfillment fees are significantly higher than standard FBA fees. A standard-size item that costs $3.22 to fulfill via FBA might cost $6.00 or more via MCF. The premium varies by size tier and delivery speed.
• Branding limitations: MCF packages come in Amazon-branded or unbranded boxes. You cannot include custom inserts, branded tissue paper, or any packaging that builds your brand experience. For DTC brands where unboxing matters, this is a meaningful drawback.
• Slower processing: MCF orders typically have longer processing times than direct FBA orders. Amazon prioritizes Amazon.com orders in their fulfillment centers. During peak season, MCF orders may experience additional delays.
• No returns through Amazon: MCF orders are not eligible for Amazon's customer returns system. You need to handle returns for non-Amazon orders yourself, which adds operational complexity.
• Inventory cannibalization: Every unit fulfilled through MCF is a unit that is not available for Amazon orders. During high-demand periods, using MCF can cause stockouts on Amazon where the same inventory would generate higher revenue due to Prime conversion rates.

MCF Cost Comparison

For a standard-size item weighing 12 ounces, here are representative 2026 MCF fees:

• Standard delivery (3-5 days): $5.85 per unit
• Expedited delivery (2 days): $8.40 per unit
• Priority delivery (next day): $11.20 per unit

Compare this to the FBA fulfillment fee for the same item on an Amazon order: approximately $3.22. The MCF premium is $2.63 to $7.98 per unit depending on delivery speed. For high-margin products, this premium may be acceptable. For low-margin products, it makes MCF uneconomical compared to fulfilling from your own warehouse or a 3PL.

When MCF Makes Sense

MCF is best suited for sellers who do not have their own warehouse or 3PL, whose non-Amazon volume is relatively low (less than 20 to 30% of total orders), and whose products have margins that absorb the MCF premium. If your non-Amazon sales represent a significant portion of your business, you are almost always better off with a hybrid approach: FBA for Amazon orders, and your own warehouse or 3PL for other channels. This avoids MCF fees, gives you branding control, and prevents Amazon order fulfillment from competing with your other channels for the same inventory.

Automating Amazon Inventory Management

Manual amazon inventory management breaks down as you scale past 100 SKUs or add a second sales channel. The velocity of decisions, when to reorder, how much to send to FBA, when to fix a stranded listing, how to split inventory across channels, exceeds what a person can monitor in spreadsheets. Automation is not optional for multi-channel sellers. It is a prerequisite for maintaining healthy IPI scores and avoiding costly mistakes.

Reorder Alerts

Set automated alerts that trigger when FBA inventory for any SKU drops below its reorder point. The reorder point should be calculated as:

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

For FBA, lead time includes your supplier lead time plus transit to your warehouse plus prep time plus transit to Amazon plus Amazon receiving time. Amazon receiving averages 5 to 14 days for standard shipments and can spike to 21 or more days during Q4. Build the worst-case receiving time into your lead time calculation so you are never caught waiting for Amazon to check in a shipment while your listing goes out of stock.

Configure alerts at two thresholds: a warning at 14 days of supply remaining (to initiate the purchase order) and a critical alert at 7 days of supply remaining (to expedite if the PO has not been placed). For your top 20 SKUs by revenue, consider a third alert at 21 days that triggers automatic PO creation with your supplier.

Auto-Replenishment Flows

The next level beyond alerts is automatic replenishment. An auto-replenishment workflow does the following without manual intervention:

1. Monitors FBA and FBM inventory levels against reorder points for every SKU, updated daily.
2. When a SKU hits its reorder point, generates a purchase order to the assigned supplier for the calculated replenishment quantity.
3. Tracks the PO through supplier confirmation, production, and shipment.
4. When inventory arrives at your warehouse, triggers FBA shipment plan creation for the appropriate quantity based on current FBA capacity and sell-through rate.
5. Sends the FBA shipment and monitors Amazon receiving, alerting you if receiving takes longer than expected.

This end-to-end flow eliminates the most common cause of FBA stockouts: delayed human decision-making. The gap between when inventory should be reordered and when someone actually places the order is where most stockouts originate.

Syncing Amazon Stock With Other Channels

For sellers on Amazon, Shopify, eBay, Walmart, and other marketplaces, inventory synchronization is the operational backbone of multi-channel selling. Every sale on any channel must immediately update available inventory across all channels to prevent overselling.

The architecture that works is a central inventory hub that acts as the single source of truth. When a sale occurs on Amazon, the hub decrements the shared pool and pushes updated available quantities to Shopify, eBay, and every other connected channel. When a sale occurs on Shopify, the same process runs in reverse.

Critical implementation details for Amazon specifically:

• FBA inventory is separate: Inventory stored at Amazon FBA should be tracked as a separate pool from your warehouse inventory. Do not try to unify them into a single count. Amazon manages FBA quantities, and your OMS manages warehouse quantities. The central hub shows both pools and calculates total available-to-promise.
• SP-API latency: Amazon's Selling Partner API processes inventory updates asynchronously. There is a 5 to 15 minute delay between when you push an update and when it reflects on the listing. During high-velocity sales periods, this latency creates an overselling window. Mitigate it with channel-specific safety buffers, hold back 5 to 10% of available inventory on Amazon to account for the sync gap.
• Order notification delays: Amazon order notifications via SP-API can be delayed by 1 to 5 minutes. Your sync system should poll for new orders frequently (every 2 to 3 minutes minimum) to minimize the window between when a sale happens and when your central inventory decrements.

FBA Shipment Planning Automation

Creating FBA inbound shipments manually through Seller Central is time-consuming for sellers with large catalogs. Automation can handle shipment plan creation, box content information, and carrier booking through the SP-API's Inbound Shipment endpoints.

An automated shipment planning workflow should:

• Calculate the optimal replenishment quantity per SKU based on current FBA inventory, sales velocity, remaining capacity, and the target days-of-supply (30 to 60 days).
• Generate the shipment plan via SP-API, including case-pack information and prep instructions.
• Print shipping labels and box content labels automatically.
• Track shipment status from creation through Amazon receiving and alert if receiving is delayed beyond expected timelines.

For multi-channel sellers, the shipment planning automation should factor in inventory needs across all channels. If your Shopify store and Amazon are both selling a product and Shopify demand is increasing, the automation should reduce the FBA allocation slightly to preserve warehouse inventory for Shopify fulfillment. This cross-channel awareness is what separates a basic Amazon replenishment tool from a true multi-channel inventory management system.

Building a Sustainable Amazon Inventory Operation

Effective amazon inventory management in 2026 comes down to three things: maintaining your IPI score above 550 to maximize capacity, keeping inventory in the 30-to-60-day supply sweet spot that avoids both low-inventory fees and aged inventory surcharges, and automating the operational workflows that maintain these targets across hundreds or thousands of SKUs.

For Amazon-only sellers, this means getting disciplined about excess inventory, stranded listings, and replenishment cadence. For multi-channel sellers, it means treating Amazon as one node in a broader inventory network, important but not the only consideration when making allocation and replenishment decisions.

The sellers who win on Amazon in 2026 are not the ones who send the most inventory to FBA. They are the ones who send the right amount of the right products, keep their IPI scores high, use FBM as a strategic complement, and automate the operational overhead that would otherwise consume their time. Start with your IPI score, build automated reorder workflows, and expand from there. The infrastructure you build for Amazon inventory management becomes the foundation for scaling across every sales channel you add.