Most sellers budget for Amazon’s fulfillment fee and forget storage. That is a mistake, because storage is the one FBA cost that grows while you do nothing. A unit that sells in three weeks costs you almost nothing to store. The same unit sitting for eleven months can accumulate more in storage charges than it earns in margin.

The structure changed meaningfully heading into 2026. The old twice-yearly long-term storage fee is gone, replaced by a monthly aged inventory surcharge that starts biting far earlier. Combined with the storage utilization surcharge and Q4 peak pricing, a single overstocked SKU can now be hit by three charges in the same month.

This guide breaks down what each charge is, when it triggers, and the specific actions that reduce it.

The four storage charges, and how they stack

Amazon storage is not one fee. It is four separate calculations applied to the same inventory, and they compound rather than replace each other.

Base monthly storage

The foundation charge, assessed on average daily cubic feet. In 2026 standard-size inventory runs roughly $0.78 per cubic foot from January through September, rising to about $2.40 per cubic foot in Q4. Oversize sits lower per cubic foot — approximately $0.56 and $1.40 respectively — but oversize items consume far more volume, so the total is usually higher.

Note the Q4 multiple: storage costs roughly three times as much in October through December. Inventory that arrives in September and does not sell until January pays peak rates for three full months.

Aged inventory surcharge

This is the charge that caught sellers off guard. It is assessed monthly, escalates by age band, and is billed on whichever is greater — a cubic-foot rate or a per-unit rate. Rates increased again in January 2026.

The escalation is steep. Inventory in the longest age bands can attract rates several times the base monthly storage charge, which means a slow-moving unit eventually costs more to store each month than it did to manufacture. Published thresholds vary by source and by category, so confirm your own bands in Seller Central rather than relying on a general figure.

Storage utilization surcharge

Applied when your inventory level is high relative to how fast you sell. The measure is days of supply: total units on hand divided by your daily sales rate. Cross roughly 22 weeks of supply and the surcharge kicks in, scaling upward the further past the threshold you sit.

This charge is independent of unit age. A seller who ships a massive restock of a brand-new SKU can incur it immediately, before any unit is a single day old.

Where the money actually goes: a worked example

Take a standard-size SKU, 0.4 cubic feet per unit, 500 units on hand, selling 3 per day (167 days of supply).

The pattern matters more than the precise numbers. The same 200 cubic feet can cost $156 or several multiples of that, determined entirely by age and velocity. Nothing about the product changed.

All figures are indicative and subject to Amazon’s published fee schedule, category, size tier and effective date. Verify current rates in Seller Central.

Seven ways to cut your storage bill

1. Manage to days of supply, not units

Stop thinking in unit counts and start thinking in weeks of cover. Target 8 to 12 weeks of supply for steady sellers. That keeps you comfortably below the utilization threshold while leaving buffer for demand swings and inbound delays.

2. Reduce cubic feet before reducing units

Storage is billed on volume, not count. Shrinking a carton’s outer dimensions by 15 percent cuts your storage bill by roughly 15 percent on every unit, every month, forever. Right-sizing packaging is the single highest-leverage change available, and it reduces fulfillment fees too when it moves a SKU into a smaller size tier.

3. Time inbound shipments against Q4 rates

Since Q4 storage costs roughly three times the off-season rate, the goal is to have peak inventory arrive close to when it sells — not months ahead. Sending Q4 stock in August means paying peak rates on units that sit through October and November. Staggered inbound shipments in September and October usually cost less overall, even accounting for placement fees.

4. Use a hybrid FBA and FBM model for slow SKUs

Not every SKU belongs in FBA. Slow movers, seasonal tails and long-tail variants often cost more in storage than the Prime badge is worth. Keep fast movers in FBA and fulfill slow SKUs yourself or through a 3PL, where storage is typically billed at lower rates without age-based penalties.

5. Act before the age threshold, not after

Once a unit crosses an aged band, the surcharge applies every month until it moves. Set an alert at roughly 120 days and act then: run a promotion, adjust price, bundle it, or arrange a removal order. Removal typically costs a fraction of a single month’s aged surcharge on a stalled unit, and it stops the bleeding permanently.

6. Use upstream storage for buffer stock

Amazon Warehousing and Distribution, or a 3PL, holds reserve inventory at lower storage rates and feeds fulfillment centers as needed. You keep coverage for demand spikes without parking the whole quantity in the highest-cost storage tier. For seasonal businesses the savings are substantial.

7. Audit your storage report monthly

The FBA Inventory Age and Storage Fee reports show exactly which SKUs are accruing which charges. Sort by fee contribution rather than unit count — storage costs concentrate heavily, and it is common for a handful of SKUs to drive the majority of the bill. Fixing those few is where the return is.

The decision that actually matters

Most storage overspending traces back to one habit: ordering in quantities that optimize unit cost from the supplier rather than total cost to sell. A 20 percent volume discount on a purchase order looks good on paper and turns negative once the excess sits eleven months accruing monthly surcharges.

Run the math on total landed and carried cost before committing to a large order. Multiply the expected months on hand by the storage rate, add the surcharge bands you will likely cross, and compare that against the supplier discount. On slower SKUs, the smaller order frequently wins.

Bottom line

FBA storage is the cost that punishes inaction. Base monthly charges are manageable; the aged inventory surcharge, utilization surcharge and Q4 peak pricing are what turn a modest line item into a margin problem. All three are driven by decisions you make upstream — order quantity, carton size and inbound timing.

Watch days of supply, right-size your packaging, stagger Q4 inbound, and clear aged units before they cross a band. At HereWeShip we help ecommerce sellers model total fulfillment cost across FBA, 3PL and self-fulfilled channels so inventory sits where it costs least. Get in touch before your next purchase order.

Fee amounts and thresholds in this article are indicative and change with Amazon’s published schedule. Confirm current rates and your own age bands in Seller Central.