Which product is paying your Amazon storage fee? Read the Monthly Storage Fees report before October
The FBA storage fee shows up in your payments as one monthly charge. It is not tied to an order, so it does not tell you which product caused it. For most of the year that is an annoyance. From October to December Amazon charges a higher monthly storage rate, and a product that sits in the warehouse costs more than it did in September.
The split by product exists. It is in one report, and every claim below points at a column in it.
Where the report is
Seller Central, Reports, Fulfillment, then in the Payments group the Monthly Storage Fees report. Pick the month you want to look at.
These columns matter:
- asin, fnsku, product_name. Which product.
- fulfillment_center. Which warehouse the units were in.
- product_size_tier. The size tier Amazon put the product in.
- item_volume, volume_units. How much space one unit takes. Cubic feet in the US, cubic metres in Europe.
- average_quantity_on_hand. How many units were stored, as an average over the month.
- estimated_total_item_volume. The space all those units took.
- month_of_charge. The month the fee is for.
- base_rate. The rate per unit of volume for that month and size tier.
- estimated_monthly_storage_fee. What this row costs.
One row is not one product
The report has a row for every product in every fulfilment centre it was stored in. In one account we looked at, a single product appeared in 92 rows for one month, because its units were spread across 92 warehouses.
If you read the first row for a product, you see a fraction of its fee. Group the rows by asin and add up estimated_monthly_storage_fee before you compare products.
The same goes for average_quantity_on_hand. It is an average, so you will see values like 0.26 or 5.55. A unit that was in a warehouse for a week counts as a fraction of a unit for the month. Add these up per product too, if you want to know how much stock you were paying for.
Why October matters
base_rate depends on the month_of_charge. The monthly rate is higher from October to December than in the rest of the year, so the same stock on the same shelf costs more in those three months. Nothing in your listing or your sales changes. Only the month does.
Compare the base_rate in your September report with the one in October when it comes out. That difference is what every slow-moving unit will cost you until January.
The number that tells you something
The storage fee on its own is not good or bad. A product that sells a lot needs a lot of stock, and pays a lot of storage. The useful number is the storage fee divided by the units you sold of that product in the same month.
A product with a small fee and almost no sales can cost you more per sale than your best seller. That is the one to look at before October: send fewer units, run a promotion to move what is there, or remove it if it will not sell before the end of the year.
Two traps
The report is an estimate. The column is called estimated_monthly_storage_fee. The amount actually charged is in your payments. Add up the report for a month and compare the total with the storage charge in your payments for the same month. If they are far apart, check that you downloaded the right month.
Size tier changes the fee, not only the volume. Two products with the same volume can pay different rates if they are in different size tiers. If a product's product_size_tier surprises you, check its dimensions in the longest_side, median_side and shortest_side columns. A measurement that is too large makes every month more expensive.
Ten minutes a month
Download the Monthly Storage Fees report for last month. Group it by asin and sum estimated_monthly_storage_fee. Put next to each product the units you sold in the same month. Sort by storage fee per unit sold.
The top of that list is where your storage money goes. Before October, it is worth deciding what happens to it.