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Card class: Sensitivity • Category: FBA Economics

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At a glance

What Amazon charges you to hold your inventory in its fulfilment centres for the period. Monthly storage is billed per cubic foot (or cubic metre) of space your units occupy, and it rises sharply in the Q4 peak months when Amazon raises the per-unit-volume rate. This card is the cash cost of slow-moving and over-stocked inventory, the line that quietly grows when product sits. It is a finance and owner card because storage fees eat margin without ever appearing in the customer-facing funnel.
What it countsTotal FBA monthly storage fees charged in the period, the per-volume charge Amazon levies for warehousing your sellable and unfulfillable units. Long-term storage surcharges on aged stock are related but tracked separately.
DriverVolume occupied times the per-volume rate times days held. Bulky, slow-selling, or over-stocked ASINs dominate. A small number of oversized SKUs can account for most of the bill.
SeasonalityAmazon raises the storage rate steeply in the Q4 peak period (typically October to December). The same inventory costs materially more to hold in those months, so a quarter-on-quarter rise is partly seasonal, not purely an over-stock signal.
Relationship to long-term storageThis card is the recurring monthly charge. Aged-stock surcharges are captured by ASINs Approaching Long-Term Storage and feed Stranded Inventory Value.
Fulfilment scopeFBA only. FBM stock is held in your own or a 3PL warehouse and is not in this number.
ChartKPI value for the period.
UnitCurrency.
Time window30D.
Alert trigger+25% vsP (a 25% or greater rise versus the prior period).
Rolesowner, finance

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Calculation

Calculated automatically from your Amazon Seller Central data. See the At a glance summary above for what the metric tracks and the worked example below for a typical reading.

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Worked example

A UK homeware brand on FBA with a mix of small, fast-moving accessories and a few bulky seasonal items. Period: 01 Apr 26 to 30 Apr 26 (30D), compared against the prior 30D.
Inventory groupShare of volumeStorage fee (illustrative)
Small fast movers (high turn)35%£210
Mid-size steady sellers30%£390
Bulky seasonal stock (low turn)25%£640
Aged / slow-moving units10%£310
FBA Storage Fees (this card)100%£1,550
This period   =  £1,550
Prior period  =  £1,180
Change vsP    =  +31.4%   (above the +25% alert threshold → card raised)
Three things to notice:
  1. A 31% rise crosses the alert. The card raises because storage is up more than 25% versus the prior period. The job now is to work out whether this is seasonal rate change, an over-stock event, or aged inventory piling up. Check the calendar first: a rise into the Q4 peak window is partly the rate, not your behaviour.
  2. Bulky low-turn stock is the real cost driver. The seasonal bulky group is only 25% of units by count but 41% of the storage bill, because storage is charged on volume and held days, not on unit count. Slow-moving oversized SKUs are where to look first.
  3. Aged stock is a double cost. The 10% aged group is paying recurring storage here and is heading toward the long-term storage surcharge. Cross-check ASINs Approaching Long-Term Storage and consider a removal, liquidation, or price action before the surcharge lands on top.
The action: split the rise into seasonal-rate versus over-stock, identify the two or three bulky slow movers driving most of the bill, and decide whether to slow inbound, run a price promotion to lift sell-through, or remove aged units. Pair with Days of Cover (avg) to confirm the over-stock read.

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Sibling cards merchants should reference together

Storage fees rarely move alone. Read them alongside:
CardWhy pair it with FBA Storage Fees
FBA FeesThe broader FBA cost line (fulfilment plus storage). Storage is one component; this card isolates it.
ASINs Approaching Long-Term StorageAged stock that is about to attract the long-term surcharge on top of recurring storage. The early-warning partner.
Stranded Inventory ValueStock you are paying to store but cannot sell because the listing is inactive or suppressed. Pure waste.
Days of Cover (avg)Confirms whether a storage rise is an over-stock problem. High cover plus rising storage means too much inventory sitting.
Sell-Through Rate (FBA)The flow side. Slow sell-through plus rising storage is the classic over-stock pattern.
Fees % of RevenuePuts storage in context against revenue. Storage rising while revenue is flat is a margin warning.

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Reconciling against Amazon Seller Central

Where to look in Seller Central: The closest Amazon-native view is:
Seller Central → Reports → Payments → Transaction view (filter for storage fee) and the Monthly Storage Fees report under Reports → Fulfilment. The Inventory Age and FBA Inventory reports help attribute the fee to specific ASINs.
Amazon bills monthly storage in arrears, usually between the 7th and 15th of the following month, for the prior month’s storage. The Monthly Storage Fees report is the authoritative per-ASIN breakdown. Timing and reporting-lag table:
TopicDetail
Billing timingMonthly storage is charged in arrears for the prior month. A 30D card window may straddle the boundary between one month’s accrual and the next month’s billing event.
Estimate vs finalBefore the monthly charge posts, the figure is an estimate based on average daily volume. The final billed amount can differ slightly once Amazon completes its measurement.
Peak-period rateAmazon’s higher Q4 storage rate applies to the peak months; a rise into that window is partly the rate change, not a volume change.
Long-term surchargeAged-inventory surcharges are a separate line and are not in this card. They show on the related cards.
Why our number may legitimately differ from Seller Central:
ReasonDirectionWhy
Accrual vs billed dateDiffers near month boundaryAmazon accrues storage daily but bills monthly. The card’s 30D window may not align with Amazon’s calendar-month billing period.
Estimate vs finalSmall differencesPre-billing estimates use average daily volume; the final charge uses Amazon’s own measured volume.
Long-term storageOurs lower if separatedIf the long-term surcharge is tracked on a separate card, this card alone will read lower than a Payments view that lumps all storage lines together.
Cross-connector reconciliation:
CardExpected relationshipWhat causes legitimate divergence
3PL / warehouse cost (other connectors)Different warehouses. FBA storage is Amazon’s charge for Amazon’s centres. FBM stock held in your own or a 3PL warehouse has its own, separate cost.A multichannel seller should not expect FBA storage to relate to 3PL cost; they are independent cost centres for different stock pools.

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Known limitations / merchant FAQs

Why did my storage fees jump even though I did not add much stock? Most likely the Q4 peak rate. Amazon raises the per-volume storage rate steeply for the peak months, so the same inventory costs materially more to hold. Check the calendar before assuming an over-stock problem. A genuine over-stock rise will also show as rising Days of Cover (avg). Why are a few SKUs responsible for most of my storage bill? Storage is charged on volume and days held, not on unit count. A handful of bulky, slow-moving SKUs can dominate the bill even if they are a small share of your catalogue by item count. Identify them in the Monthly Storage Fees report and decide whether to slow inbound, promote, or remove them. Is long-term storage included in this number? No. This card is the recurring monthly storage charge. Aged-inventory surcharges are tracked separately by ASINs Approaching Long-Term Storage. When Payments lumps both lines together, this card can read lower than that combined view. The card raised on a +25% rise. Is that always a problem? Not always. A seasonal rate change can trip the threshold without any change in your behaviour. The alert is a prompt to investigate, not a verdict. Split the rise into rate versus volume before acting. How do I reduce this number? Improve sell-through on slow movers, slow or pause inbound on over-stocked SKUs, remove or liquidate aged units before the long-term surcharge applies, and review whether any bulky low-turn items are better fulfilled FBM. Pair this card with Sell-Through Rate (FBA) and Stranded Inventory Value.

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Tracked live in Vortex IQ Nerve Centre

FBA Storage Fees is one of hundreds of KPI pulses Vortex IQ tracks across Amazon Seller Central and 70+ other ecommerce connectors. Nerve Centre runs the detection layer; Vortex Mind investigates the cause when something moves; Ask Viq lets you interrogate any number in plain English. Start for free or book a demo to see this metric running on your own data.