Amazon's Inventory Fee Trap: Too Much and Too Little

Amazon has two fees that pull in opposite directions. One punishes you for holding stock too long. The other punishes you for holding too little. Most advice treats them separately, which is how sellers end up solving one by walking straight into the other.

They are worth understanding together, because the safe zone between them is narrower than it looks, and Q4 compresses it further.

The fee for too little: low inventory level

The low-inventory-level fee applies when your trailing 30-day and trailing 90-day historical days of supply are both below 28 days. Both windows have to be under the line. One bad month alone won't trigger it.

Days of supply is your average daily inventory at fulfillment centers divided by your average daily units sold. Since January 2026 it is measured at FNSKU level, meaning each individual variation is judged on its own rather than rolled up to the parent. If you sell one colour hard and three colours slowly, the fast one can be charged while the parent looks perfectly healthy.

The 2026 rates, per unit sold, are roughly:

Days of supply	Small standard	Large standard under 3lb	Large standard 3–20lb
0–13 days	$0.89	$0.97	$1.11
14–20 days	$0.63	$0.70	$0.87
21–27 days	$0.32	$0.36	$0.47

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

You are exempt if the parent ASIN is within 180 days of its first inventory receipt, if you are within roughly your first year of selling with FBA, if the product sold fewer than 20 units in the trailing seven days, if it is a grocery product, or if the SKU is mainly replenished through Amazon Warehousing and Distribution.

Here is the detail that costs people money: inventory in transit does not count. Only stock actually received and available sits in the numerator. Your container on the water, your shipment sitting in an Amazon receiving queue, your units at a prep center — none of it helps. Sellers who plan to the arrival date rather than the received-and-live date get charged for a shortage they have already paid to fix.

There is no seasonal exemption. You cannot flag a Q4 run-down as intentional.

The fee for too long: aged inventory

The aged inventory surcharge starts at 181 days and steps up as units get older. It is charged monthly, on top of your normal storage fee, based on a snapshot taken on the 15th of each month, with charges posting between roughly the 18th and 22nd.

The 2026 bands, effective January 16, 2026:

Days in fulfillment center	Per cubic foot	Per-unit minimum
181–210	$0.50	—
211–240	$1.00	—
241–270	$1.50	—
271–300	$5.45	—
301–330	$5.70	—
331–365	$5.90	—
366–455	$6.90	$0.30
456+	$7.90	$0.35

Look at what happens between day 270 and day 271. The rate goes from $1.50 to $5.45 per cubic foot, a jump of about 3.6x, and then barely moves for the next three months. Every other step on that table is gentle. That one is a cliff.

Clothing, shoes, bags, jewelry and watches are exempt from the 181–270 bands and start at the 271 tier.

Two things follow from how this is measured.

Amazon ages units first-in, first-out across the whole network. So a product that sells steadily can still be accumulating a surcharge, because the oldest units in the pile keep getting older while the newer ones ship. Healthy sell-through on a SKU does not mean you have no aged units in it. Sellers routinely check their sales velocity, conclude the product is fine, and get billed anyway.

And because the assessment is a monthly snapshot on the 15th, the cost of being late is lumpy rather than gradual. Units that cross day 271 the day before a snapshot are charged at $5.45 per cubic foot for that whole month. A removal order placed a week earlier would have cost you the removal fee instead. This is one of the few places on Amazon where a decision taken on a Tuesday rather than the following Tuesday changes the bill by several multiples.

Why the gap is narrower than it looks

The two fees rarely hit the same SKU in the same month, because a SKU with a big aged tail usually has plenty of days of supply. They hit the same business in the same month, constantly. And the fix for one pushes you toward the other.

Cut your reorder quantities to avoid aging, and the fast movers dip under 28 days. Send more to protect the fast movers, and the slow tail ages past 181 days. The genuinely safe operating window sits somewhere around 30 to 60 days of cover, and it has to be judged per variation, not per product.

Q4 tightens it from a third direction. Monthly storage for standard-size items runs about $0.78 per cubic foot from January to September and about $2.40 from October to December. Oversize goes from roughly $0.56 to $1.40. So the same overstock that was mildly annoying in August is roughly three times as expensive to hold in November, while the low-inventory fee gives you no room to run lean instead.

What to do about it

1. Work at variation level, not parent level. Both fees are assessed on individual SKUs. A healthy parent average hides the two children that are actually being charged.
2. Find your day-181 and day-271 populations now, not on the 15th. The question is not "how much stock do I have" but "how old is the oldest of it". Those are completely different numbers and only one of them is on your dashboard by default.
3. Treat day 271 as a hard date. If units will cross it before they sell, price them down, bundle them, or remove them. Discounting to clear at day 250 is usually cheaper than holding at $5.45 per cubic foot.
4. Plan cover from the date stock is receivable, not shippable. Add your real receiving lag. In-transit units do not protect you from the low-inventory fee.
5. Check the exemptions before panicking. New parent ASINs, first-year FBA sellers, products under 20 units a week and grocery are outside the low-inventory fee entirely.

The honest summary

Neither of these fees is huge on its own. A few cents to a couple of dollars a unit does not sound like a crisis. They matter because they are structural: they are charged on the products that are working, every month, quietly, and they are the two costs most likely to be missing from the margin figure you make decisions with.

The trap is that they are usually managed reactively. You notice the aged surcharge on a statement, clear stock, and three months later get the low-inventory fee on the same catalogue. The window between them is real, but it is narrow enough that you cannot hold it by instinct across a few hundred SKUs.

That is a monitoring problem more than a strategy problem, and it is what Seller Sphere is for. It tracks stock cover and inventory age per variation and flags the SKUs approaching either edge, so you get to act before day 271 rather than read about it on a statement.

Frequently asked questions

What is Amazon's low-inventory-level fee? A per-unit fee charged when a product's trailing 30-day and trailing 90-day historical days of supply are both below 28 days. In 2026 it ranges from about $0.32 to $1.11 per unit across standard size tiers, and up to roughly $2.09 for bulky products.

Does inventory in transit count toward my days of supply? No. Only inventory that has been received and is available at fulfillment centers counts. Stock on the water, in a prep center, or waiting in Amazon's receiving queue does not protect you from the low-inventory-level fee.

When does Amazon's aged inventory surcharge start? At 181 days in a fulfillment center. It is charged monthly on top of standard storage fees, based on a snapshot taken on the 15th of each month.

Why is day 271 important? Because the surcharge jumps from $1.50 per cubic foot in the 241–270 band to $5.45 in the 271–300 band, roughly a 3.6x increase in a single step. The steps before and after it are far smaller, which makes 271 the single most expensive day to cross.

How does Amazon decide how old my inventory is? On a first-in, first-out basis across its entire fulfillment network. This means a steadily selling product can still be accruing aged-inventory surcharges on its oldest units, so good sell-through does not guarantee you are not being charged.

Who is exempt from the low-inventory-level fee? Parent ASINs within 180 days of first inventory receipt, sellers within roughly their first year using FBA, products selling fewer than 20 units in the trailing seven days, grocery products, and SKUs primarily replenished through Amazon Warehousing and Distribution.

How much more does storage cost in Q4? Monthly storage for standard-size items rises from roughly $0.78 per cubic foot between January and September to about $2.40 between October and December. Oversize rises from about $0.56 to $1.40.