Running out of FBA stock does more than pause sales. When your inventory stays thin relative to what you have been selling, Amazon can add a low-inventory-level fee on top of the normal FBA fulfillment fee for units it ships.
This fee is about being understocked, not about inventory that sat too long. Long-term storage and aged inventory surcharges punish aging stock. The low-inventory-level fee punishes the opposite problem: historical days of supply that stay below Amazon's 28-day line.
In this article, you'll learn how historical days of supply works (30-day and 90-day), where to see it on the FBA Inventory page, who Amazon exempts, how sellers minimize the fee by restocking, and what changed for 2026 according to Amazon and reputable fee trackers. Always verify current rates in Seller Central before you plan around a number.
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In a Seller Forums explanation, Amazon said the fee exists because low inventory relative to demand makes it harder to place products across the fulfillment network, which can slow delivery and raise shipping costs. The charge is added to the FBA fulfillment fee for shipped units of eligible products.
Amazon calculates the fee from historical days of supply: inventory levels relative to actual historical sales. That is different from long-term storage fees, which apply when inventory ages in the network. Our guide to avoiding long-term storage fees covers the aging-inventory side. This post is only about the understocked side.
Amazon also said it will only charge the fee when historical days of supply is below 28 days, and only when both the short-term measure (last 30 days) and the long-term measure (last 90 days) are below that line. If either window is at 28 days or above, the fee does not apply. That gives you two ways out: improve short-term stock quickly, or manage inventory so the 90-day picture stays healthy.
In Seller Forums answers, Amazon described historical days of supply as average daily inventory units on hand divided by average daily shipped units, measured over both the last 90 days and the last 30 days.
Amazon's forum walkthrough used a sample product where the short-term figure was below 28 days but the long-term figure came out to 42.0 days. That product would not incur the fee, because both windows must be under 28 days. The same logic applies in reverse: a thin week does not trigger the fee if the 90-day average is still above the line.
On the FBA Inventory page, Amazon shows a Historical days of supply column. Amazon said that column displays the greater of the short-term and long-term metrics. If that displayed value is greater than 28, the fee is not applied. You can hover the details link to preview the calculation for a product, search by SKU or ASIN, and sort the column ascending to find products closest to the fee.
Inbound units typically do not count until they are received as sellable inventory, and the metric may update weekly. Plan replenishment with that lag in mind.
Amazon's original Seller Forums explanation said historical days of supply was calculated at the parent-product level, so variations under the same parent shared the metric. In a later Seller Forums reply about fluctuating fulfillment fees, Amazon staff also described calculating the metric at the product FNSKU level and adding the fee to FBA fulfillment for shipped units of eligible products.
Secondary fee trackers (including Goat Consulting) describe a January 15, 2026 update: calculation at seller-FNSKU level, coverage for small and large bulky as well as standard-size, and a Grocery exemption. Goat also publishes example 2026 rates by size tier and days-of-supply band (for example, small standard listed from $0.32 in the 21 to under-28-day band up to $0.89 in the 0 to under-14-day band). Treat those dollars as secondary and confirm the live rate card in Seller Central.
Amazon's 2026 U.S. Referral and FBA fee update said FBA fees would rise by an average of about $0.08 per unit, that no new fee types were introduced, and that changes were generally effective January 15, 2026.
Amazon's Seller Forums FAQ stated that the fee applies to standard-sized products when both long-term and short-term historical days of supply are less than 28 days. Later Seller Forums posts quoting current help text also list Small and Large Bulky products under the same 28-day rule. Always open the current help article in Seller Central for the size tiers that apply to you today.
Amazon listed these exemptions in that same FAQ:
Secondary sources also report a Grocery category exemption after the January 2026 updates. If you sell Grocery, verify that exemption on Amazon's current help page rather than relying on a third-party summary alone.
Low-inventory fees, storage, and fulfillment all hit margin. Bubba Academy's step-by-step program shows Amazon sellers how to plan inventory and launch without guessing.
Amazon pointed sellers to the FBA Inventory page:
When fulfillment fees look higher than expected, check Payments > Transaction View. The low-inventory-level fee is added to the fulfillment line for shipped units. If lost or damaged stock drove you under the line, see our guide to FBA reimbursements.
Amazon's own advice is straightforward: for products you replenish yourself, send enough additional units that the product's short-term (last 30 days) historical days of supply exceeds 28 days. When the short-term metric clears 28 days, the fee does not apply, even if the long-term metric is still below.
Practical habits that match that rule:
Amazon and secondary sources describe the fee as tiered by how far below 28 days you sit (deeper shortages cost more). Forum answers summarized bands such as 0–14 (highest), 14–21, and 21–28 (lowest), with no fee above 28. Confirm exact dollars in Seller Central.
The low-inventory-level fee is Amazon's charge for running too lean for too long relative to your own sales history. It is not a long-term storage fee, and it is not automatic every time your on-hand count looks low for a day or two.
The key takeaways:
Your next step: Open FBA Inventory, sort Historical days of supply ascending, and pick every SKU under 40 days. For each one under 28, create or accelerate an inbound shipment sized to push the 30-day metric back above the line, then re-check after the weekly metric update.
Bubba Academy trains sellers on product research, Brand Registry, listings, FBA, ads, and pricing, including how to plan inventory so fees and stockouts do not eat your margin.
Join Bubba Academy Today →Amazon charges it only when both the short-term (last 30 days) and long-term (last 90 days) historical days of supply are below 28 days. If either window is 28 days or higher, the fee does not apply.
Amazon describes it as average daily inventory units on hand divided by average daily shipped units, measured over the last 30 days and the last 90 days. The FBA Inventory column shows the greater of those two figures.
Go to the FBA Inventory page. Use the Historical days of supply column, hover details for the calculation preview, and sort ascending to find products near or under 28 days.
Amazon lists new Professional sellers for 365 days after first inventory received, new-to-FBA parent products for 180 days with FBA New Selection enrollment, and products auto-replenished by Amazon Warehousing and Distribution under the AWD rules stated in help. Confirm Grocery and size-tier rules on the current help page.
No. Long-term storage and aged inventory charges apply when inventory sits too long. The low-inventory-level fee applies when historical days of supply stay too low relative to your sales. You can face one, the other, both, or neither depending on how you stock each SKU.