Most FBA fees punish you for holding too much inventory. The Amazon low-inventory-level fee does the opposite: it charges you for holding too little. If a product sells well but you keep it lean, Amazon adds a per-unit fee on every unit that ships — on top of the standard fulfillment fee you already pay.

For 2026 the mechanics changed in a way that catches a lot of sellers off guard. The fee is no longer measured at the parent ASIN level. It is measured per FNSKU, which means a single slow-restocking size or color can trigger charges while the listing as a whole looks perfectly healthy.

This guide covers the exact rates, the threshold that triggers them, who is exempt, and the inventory targets that keep the fee off your statement.

What triggers the fee

The fee applies when both your 30-day and your 90-day historical days of supply fall below 28 days. The word « both » is the whole game: keeping either metric above 28 days avoids the charge entirely.

Amazon assesses this weekly. Days of supply is your available FBA inventory divided by your recent daily sales velocity — so the fee can appear not because you shipped less stock in, but because the product suddenly started selling faster.

That is the counterintuitive part sellers report most often: a sales spike can create a fee. Growth without a replenishment response is the trigger.

2026 rates by size tier

The fee is charged per unit shipped, and it scales with both product size and how deep into the danger zone your days of supply fall.

Rates are indicative and subject to Amazon’s published fee schedule, which changes periodically.

Run the math on a real SKU and the scale becomes obvious. A large standard unit under 3 lb selling 1,500 units a month at 10 days of supply carries $0.97 per unit — about $1,455 a month, purely for running lean. Drag that SKU back above 28 days of supply and the line item disappears.

The January 15, 2026 change: FNSKU, not parent ASIN

This is the single most important update for 2026. Before, measurement happened at the parent ASIN level, so a healthy overall listing effectively shielded weak variations. As of January 15, 2026, assessment moved to the individual seller FNSKU.

Practically, that means every variation is now judged on its own:

• A t-shirt listing with ten sizes is now ten separate assessments, not one.
• Your best-selling size can be comfortably stocked while two sizes quietly accrue per-unit fees.
• Aggregate inventory dashboards will look fine. The fee shows up on the statement anyway.

If you sell variation-heavy catalogs — apparel, accessories, consumables in multiple counts — this change alone can move your effective FBA cost per order by several cents, and it will not be visible in a parent-level view.

Who is exempt

Several categories of product and seller fall outside the fee entirely. Check these before you change your replenishment strategy:

• New professional sellers — exempt for their first 365 days.
• FBA New Selection products — exempt for their first 180 days.
• Low-velocity products — fewer than 20 units sold in the trailing 7 days.
• Grocery category items.
• AWD-replenished inventory — stock automatically replenished through Amazon Warehousing and Distribution.

That last exemption is strategically significant. Routing replenishment through AWD removes the fee exposure on those SKUs and simultaneously reduces inbound placement complexity — two fees addressed by one structural change.

The target that actually keeps you safe

The threshold is 28 days, but managing to exactly 28 days is how sellers get charged. Sales volatility, inbound transit time and receiving delays all push your number down without warning.

A workable operating standard:

• Target 35 days of supply on the 30-day window. That gives roughly a week of buffer against a velocity spike.
• Check every Monday, since assessments run weekly. A Monday review lets you place an inbound shipment before the next assessment lands.
• Work at the FNSKU level, not the parent. Export your variation-level days of supply and sort ascending; the bottom of that list is your fee exposure.
• Account for inbound lead time. If receiving takes 10 to 14 days, a 28-day threshold means reordering at roughly 42 days of supply, not 28.
• Keep an AWD buffer on your highest-velocity SKUs so replenishment is automatic rather than manual.

Weighing it against storage costs

The obvious objection: holding more inventory costs money too. That is true, and the comparison is worth running explicitly rather than assuming one side wins.

For most steady-selling standard-size products, the per-unit fee at 0 to 13 days of supply is materially larger than the monthly storage cost on the extra weeks of stock. Running lean on a proven seller is usually the more expensive mistake.

What to do this week

Three concrete actions, in order:

• Pull a variation-level days-of-supply report and list every FNSKU under 35 days. Those are your fee candidates, regardless of how the parent listing looks.
• Cross-check that list against the exemptions above, and remove anything that genuinely qualifies.
• For what remains, calculate the per-unit fee against your monthly sell-through and compare it to storage on the additional units. Then set reorder points that include your real inbound lead time.

The fee is entirely avoidable. It costs sellers money mainly because it is measured on a metric most replenishment systems do not watch — days of supply at the variation level, assessed weekly.

The bottom line

The low-inventory-level fee rewards sellers who plan replenishment around velocity rather than around unit counts. Keep either your 30-day or your 90-day days of supply above 28, aim for 35 as a working buffer, manage it per FNSKU, and build inbound lead time into your reorder point.

Need the inbound side of this to run faster so your days of supply stay healthy? HereWeShip helps online sellers compare carriers and services on replenishment shipments, so inventory reaches fulfillment centers sooner and your stock never drifts into fee territory. Compare your inbound shipping options and keep the fee off your next statement.