Amazon Low-Inventory-Level Fee Explained (and How to Avoid It)

By Bernardo Campelo, Forbes Business Council E-Commerce Leader, Amazon SPN Certified provider, and Founder of PrepVia.

Of every fee Amazon has introduced since 2024, this is the one that produces the most confused messages in my inbox. Sellers understand storage fees: you occupy space, you pay for space. They understand the aged inventory surcharge: rent turns punitive after six months. But a fee for having too little inventory breaks the mental model that Amazon charges you for what you use.

The logic is colder than that. When your inventory runs chronically thin, Amazon cannot keep your units spread across its regional network. Orders get fulfilled from whichever fulfillment center still has stock, often three zones from the buyer, which costs Amazon transportation money and costs your listing delivery speed. The fee prices that inefficiency back to you, the same way the inbound placement fee prices the work of distributing your inbound freight. Thin stock and concentrated inbound are the same network problem from opposite ends.

I run PrepVia, an FBA prep center in Miami, Florida. Here is exactly how the fee works as of 2026: the calculation, the rates, the exemptions, the tension with the aged inventory surcharge, and the replenishment cadence that makes it a fee you never pay.

What the Low-Inventory-Level Fee Actually Is

Amazon introduced the fee on April 1, 2024, and the core mechanics have held since. The January 15, 2026 update changed two structural things: the metric is now computed per FNSKU instead of per parent ASIN, and bulky products, previously outside the fee, are now in scope, while grocery became exempt. It is not a storage charge. It is not a one-time penalty. It is a per-unit amount stacked on the normal FBA fulfillment fee, charged on every unit that ships to a customer while your days of supply sits below 28. Sell 300 units in a week while you are under, and you pay it 300 times that week.

Two mechanical details do most of the damage. First, the fee is evaluated weekly, so a bad month is four rounds of charges, not one. Second, because it is charged per unit sold, it scales with velocity: it costs the most on your best-selling ASIN during its best week, exactly when sellers are most tempted to run lean.

How Amazon Calculates Historical Days of Supply

The metric behind the fee is called historical days of supply, and the formula is plain division: your average daily inventory on hand at Amazon fulfillment centers divided by your average daily units sold. Amazon runs that division across two trailing windows at once, and the fee applies in a given week only when both results are below 28 days.

That word, both, is the only seasonal accommodation this fee has. There is no seasonal exemption checkbox anywhere in Seller Central. The dual window is the accommodation. A demand spike has to hold for weeks before the 90-day metric surrenders. That window is your time to land more stock before the charges start, if you are watching for it.

Three more mechanics inside the formula decide whether you pay:

In-transit units do not count. The numerator is inventory received and available at fulfillment centers. A shipment sitting on a truck, or sitting in an FC receiving queue for twelve days, contributes nothing. This is the single most common way sellers who did everything right still get charged: they shipped on time and check-in ate the buffer. Peak receiving times are their own subject, covered in our guide to FBA check-in times, but for this fee the rule is simple: protection begins when units are received, not when they ship.

As of January 2026, the metric lives at the FNSKU level. Through 2025 the calculation ran at the parent ASIN and variations pooled together, so a healthy sibling could carry a starved one. That cover is gone: each variation now stands on its own math, and a starved child SKU pays the fee even when the rest of the family is deep in stock.

Rising sales shrink the number while your inventory stands still. Days of supply is a ratio. If velocity doubles, your days of supply halves overnight even though the physical stock has not moved. Sellers watch units and feel safe. The fee watches the ratio.

The rate table, as of 2026

Bulky products joined the fee on January 15, 2026 with their own bands, reaching roughly $2.09 per unit at the deepest tier.

Rates are for the US marketplace as of 2026, and Amazon revises fee schedules annually, so confirm the current table in Seller Central before budgeting on it. How this fee fits into the rest of this year's schedule, including what moved and what did not, is in our 2026 FBA fee changes breakdown.

Who Is Exempt (and Who Only Thinks They Are)

As of 2026, the published exceptions are specific and narrow:

And the exemption sellers assume exists but does not: seasonality. A Halloween ASIN, a space heater, a pool float, none of them get a seasonal flag. They get the 90-day window, which absorbs the front edge of a ramp, and nothing else. If the product sells hard for three months, the 90-day metric eventually reflects peak velocity and days of supply collapses unless inventory arrives in waves timed ahead of the curve. That timing problem is the same one that governs the Q4 inbound deadlines, and Q4 is precisely when this fee and the deadline calendar squeeze from both sides at once.

The Squeeze: Two Fees Pointing at Each Other

Here is where the fee earns its reputation. The instinctive fix, ship a mountain of stock and never think about the threshold again, walks directly into a different fee coming from the opposite direction.

Add the third wall: FBA capacity limits cap your inbound at a multiple of Amazon's forecast of your sales, so you cannot park a year of inventory at Amazon even if you were willing to pay the storage. The corridor is real: enough stock to stay above 28 days, little enough that nothing crosses day 181, all inside a ceiling you do not control.

Finding the Corridor: The Days of Cover Math

The arithmetic that answers both fees at once is days of cover, and the full walkthrough lives in our days of supply guide. The short version, tuned for this fee:

The reorder point that keeps you inside the corridor is standard: daily velocity multiplied by total lead time, plus the safety buffer. The term sellers underestimate is total lead time, because it is not transit time. It is prep time plus transit plus FC check-in, and the check-in term stretches badly in Q4. A reorder point built on a five-day lead-time assumption meets reality at fifteen days in November, and the difference lands you squarely in the 21-27 day fee band.

Cadence Beats Size: What Actually Prevents This Fee

Now the operational part, which is the part I know from the warehouse floor rather than the fee schedule.

The root cause of most low-inventory-level fee charges is not underbuying. It is replenishment shape. A seller buys plenty of inventory but ships it to Amazon in giant, infrequent sends, because big shipments feel efficient: one freight booking, one prep batch, one check-in to babysit. The result is a sawtooth: days of supply spikes toward 90 at check-in, bleeds down for weeks, and the last stretch of every cycle runs below 28. The seller pays the fee on a schedule, at the tail of every cycle, while the head flirts with aging.

The objection is always freight and placement economics. But the placement fee is charged per unit, so splitting a quarterly send into three monthly sends does not multiply it. The real added cost of cadence is per-shipment freight, and for most standard-size catalogs that increment is a fraction of what the sawtooth costs at both ends.

This is the actual role of a prep center against this fee, and it is not labeling. Supplier economics want big movements: a full container, one inbound into the US. Amazon's fee structure wants small, steady arrivals. Those two facts do not have to fight. The container lands once at a prep center, and the prep center feeds Amazon in cadence-sized shipments cut against actual weekly velocity. Bulk economics on the inbound leg, corridor economics on the outbound leg. Domestic 3PL storage runs far below Amazon's storage pricing, carries no aging surcharge, and staged units, unlike units inside an FC, can still be redirected, rebundled, or pushed to another channel. Our storage and forwarding rates are on the pricing page.

Frequently Asked Questions

What is the Amazon low-inventory-level fee?

It is a per-unit fee Amazon charges when inventory relative to sales stays below 28 days of supply. Introduced in April 2024, it runs from $0.32 to $1.11 per unit sold for standard-size products as of 2026, with bulky products added in January 2026 at rates up to roughly $2.09, depending on size tier and how far below 28 days you sit. It is added on top of the regular FBA fulfillment fee for every unit shipped while the condition holds, and it is evaluated weekly.

How does Amazon calculate historical days of supply?

Amazon divides your average inventory on hand at fulfillment centers by your average daily units sold, measured over two windows at once: the trailing 30 days and the trailing 90 days. The fee applies only when both numbers fall below 28 days, and since January 2026 the metric is computed at the FNSKU level, so each variation is measured on its own. Inbound inventory that has not been received does not count, which is why slow check-ins can push you into the fee even while a shipment is already on a truck.

Which products are exempt from the low-inventory fee?

As of 2026, five groups are exempt. New parent ASINs get 180 days after the first unit is received. Sellers new to FBA get roughly their first year. Products that sold fewer than 20 units in the trailing 7 days are excluded. Grocery is exempt as of January 2026. So are SKUs replenished mostly through AWD auto-replenishment. There is no formal seasonal exemption: the 90-day window is the only mechanism that softens demand spikes. Amazon has also credited the fee back when its own receiving delays caused the shortfall, so audit your transaction reports against your check-in dates.

How do I avoid both low-inventory and aged-inventory fees?

Target a corridor of roughly 35 to 90 days of supply at Amazon instead of minimizing or maximizing stock. Replenish in smaller, more frequent shipments rather than one giant quarterly send, and stage backup inventory at a prep center or 3PL so you inbound against real sales velocity. That keeps you above the 28-day threshold on both windows without stranding units that age past day 180.