How the low-inventory-level fee checker works
Amazon compares how much stock an FBA item had with how fast it sold. The checker estimates the same two figures:
- 30-day historical days of supply = average units in stock over the last 30 days ÷ average units sold per day over the last 30 days
- 90-day historical days of supply = average units in stock over the last 90 days ÷ average units sold per day over the last 90 days
If both are below 28 days and no exemption applies, the item is at risk of the fee. The checker also suggests how many units to send: your daily sales pace (the higher of your 7-day and 30-day rate) × the days of cover you want, minus the units already available or inbound.
The rule, in Amazon’s terms
| Rule | Detail |
|---|---|
| When the fee applies | Short-term (30-day) and long-term (90-day) historical days of supply are both below 28 days |
| Items covered | Standard size, plus Small and Large Bulky from 2026 |
| Sales exemption | Fewer than 20 units sold in the past 7 days |
| New seller exemption | New Professional sellers, for 365 days after first FBA inventory is received |
| New product exemption | Parent products new to FBA, for 180 days |
| Category exemption | Grocery |
Source: Amazon Seller Central help page “Low-inventory-level fee”, checked September 2026. The fee has applied since April 1, 2024. Check the current per-unit rates on that page.
Frequently asked questions
Is the threshold 28 or 35 days?
Amazon’s help page says 28 days. Some blogs mention 35; this checker follows Amazon’s page.
Does sending a lot of stock at once fix the problem?
It stops the fee, but too much stock costs storage fees, which are higher from October to December, and inventory over 181 days old pays aged inventory surcharges. Aim for a steady level of cover.
Why is my result different from Seller Central?
Amazon uses its own daily inventory and sales records. This checker uses the averages you enter, so treat it as an estimate and check Amazon’s figures before you act.
Related guide: Amazon FBA Fees for Holiday 2026: Peak Fee, Fuel Surcharge and Low-Inventory Fee.
Last updated September 15, 2026