Overview

Amazon charges a low-inventory-level fee to sellers who consistently maintain insufficient stock relative to their sales velocity. This fee is designed to encourage sellers to keep adequate inventory levels so Amazon can distribute products efficiently across its fulfillment network. Starting April 15, 2026, Amazon is making important changes to how this fee is calculated, shifting from parent-ASIN-level to seller-FNSKU-level measurement.

Key Points for Amazon Sellers

• Calculation change effective April 15, 2026 — Amazon will now calculate the historical days of supply metric at the seller-FNSKU level rather than the parent-ASIN level, giving sellers more granular control over which specific products trigger the fee.
• 28-day threshold remains in place — The fee only applies when a product's inventory levels relative to historical demand fall below 28 days of supply. Both the short-term (30-day) and long-term (90-day) historical days of supply must be below this threshold for the fee to kick in.
• Dual-metric safeguard — If either the short-term or long-term historical days of supply is at or above 28 days, the fee will not be charged, providing sellers with a built-in safety net against temporary stock fluctuations.
• New category exemptions — The fee now applies to standard-size and large bulky products. Items classified under the extra-large category are exempt from the low-inventory-level fee.
• Slow-moving inventory exempt — Products with low sales velocity remain exempt from the fee, though sellers should be aware that slow-moving items may see reduced delivery speed promises or limited nationwide availability.

How the Fee Works

Amazon's low-inventory-level fee is tied directly to a metric called historical days of supply, which measures how many days your current inventory would last based on recent sales patterns. The system evaluates two timeframes: a short-term window covering the last 30 days and a long-term window spanning the last 90 days. Only when both of these metrics fall below 28 days will the fee be applied. This means that seasonal fluctuations or temporary stockouts won't automatically trigger additional charges as long as one of the two windows shows adequate supply levels. The fee is added on top of the standard FBA fulfillment fee for all shipped units of eligible products.