What FBA Inventory Aging Buckets Track
Inventory aging buckets are the standardized age tiers Amazon uses to classify every unit of FBA inventory by days since FBA receive date. Each unit's age clock starts the moment Amazon checks it in, regardless of when you shipped it from the manufacturer or how long it sat at AWD. The inventory aging buckets feed both fee calculations (Aged Inventory Surcharge) and account-level metrics (IPI Excess Inventory Percentage).
Amazon tracks five inventory aging buckets for the standard FBA program: 0 to 90 days, 91 to 180 days, 181 to 270 days, 271 to 365 days, and 365+ days. The first two buckets are free of aging penalties. Starting at 181 days, every unit incurs a monthly per-cubic-foot surcharge that scales aggressively the longer it stays.
Aged Inventory Surcharge by Bucket (US, 2025)
The Aged Inventory Surcharge is the monthly fee Amazon charges on inventory that sits in any aging bucket past 181 days. It is billed on the 15th of each month based on a snapshot of units in each bucket. Rates per cubic foot:
| Aging Bucket | Monthly Surcharge per Cubic Foot |
|---|---|
| 0 to 90 days | $0.00 (no surcharge) |
| 91 to 180 days | $0.00 (no surcharge) |
| 181 to 210 days | $0.50 |
| 211 to 240 days | $0.80 |
| 241 to 270 days | $1.10 |
| 271 to 365 days | $1.60 |
| 365+ days | $6.90 |
The cliff at 365+ days is intentional. Amazon wants old inventory removed from the network, so the fee jumps from $1.60 to $6.90 per cubic foot, more than 4x. Combined with the regular monthly storage fee, units in the 365+ bucket cost roughly 10x more per month to hold than fresh inventory.
Worked Example: Aged Surcharge on Slow-Moving Inventory
You have 800 units of a discontinued ASIN in FBA. Each unit is 0.04 cubic feet (small standard size). The units have aged into the 271-365 day bucket. Velocity is 15 units per week. Without intervention, what does this stranded position cost?
| Variable | Calculation | Value |
|---|---|---|
| Total cubic feet | 800 × 0.04 | 32 cubic feet |
| Monthly Aged Inventory Surcharge (271-365) | 32 × $1.60 | $51.20 |
| Monthly storage fee (Q1-Q3) | 32 × $0.83 | $26.56 |
| Total monthly holding cost | $51.20 + $26.56 | $77.76 |
| Months until 365+ bucket | (365 - 320) / 30 | 1.5 months |
| Surcharge after 365+ tip | 32 × $6.90 | $220.80 per month |
| Months to sell-through at 15/wk | 800 / (15 × 4.3) | 12.4 months |
Selling through naturally would cost $220.80 per month for the back end of the position. Total holding cost over 12.4 months: roughly $1,800. A removal order at $1.05 per unit ($840 total) plus 30% liquidation recovery on COGS is cheaper than holding through.
Why Inventory Aging Buckets Are Different on FBA
Generic ecommerce inventory aging is a soft warning. With FBA, inventory aging buckets are a hard fee schedule plus an IPI input. The Excess Inventory Percentage component of IPI directly compares units in the 91-180 day and 181-270 day inventory aging buckets against forward demand. High balances in those buckets simultaneously trigger fees and reduce restock limits.
FBA also publishes inventory aging bucket data per ASIN in the FBA Inventory Age report, available in Seller Central. Sellers should pull this report monthly and intervene before any unit crosses the 181-day line. Once a unit enters the 181-210 bucket, the only ways out are sell-through, removal, or destruction.
Common Mistakes with Inventory Aging Buckets
Watching the 365+ cliff but missing the 181 trigger. The biggest behavior change is between 180 and 181 days, when surcharges turn on. Sellers focused on the dramatic 365+ jump miss the 6 months of $0.50 to $1.10 fees that accumulate first.
Confusing FBA receive date with inventory date. Inventory aging buckets count from the FBA receive date, not the date you shipped it from your supplier. A unit sitting at AWD for 90 days resets to age 0 when it transfers to FBA.
Running removal orders too late. Removal orders take 14 to 30 days to process. A unit at day 175 that you remove on day 175 still gets one month of Aged Inventory Surcharge because it crosses 181 days during the removal queue. Plan removals 30 to 45 days before the bucket boundary.
Frequently Asked Questions
What are FBA inventory aging buckets?
FBA inventory aging buckets are the age tiers Amazon uses to classify your FBA stock: 0-90 days, 91-180 days, 181-270 days, 271-365 days, and 365+ days. Buckets older than 181 days incur the Aged Inventory Surcharge.
How does Amazon calculate the age of FBA inventory?
Amazon counts inventory age in days from the original FBA receive date. Each unit retains its receive date independently, so a bin with 200 units may have units across multiple aging buckets.
What is the Aged Inventory Surcharge?
The Aged Inventory Surcharge is a monthly fee on units in FBA more than 181 days. Rates start at $0.50 per cubic foot and scale up to $6.90 per cubic foot at 365+ days.
How do inventory aging buckets affect IPI?
Inventory aging buckets feed Amazon's Excess Inventory Percentage metric, one of three IPI inputs. High balances in the 91-180 and 181-270 buckets push your Excess Inventory Percentage up, which lowers your IPI score.