A seller moving 50,000 units a year through Fulfillment by Amazon can absorb roughly $15,500 in new annual fulfillment costs from a single, easy-to-miss rate change — without a single competitor undercutting them, without a single ad dollar wasted, and without touching their listing price. That's the quiet arithmetic behind Amazon's 2026 FBA fee changes, which took effect in mid-January and reshaped two of the least-watched line items on a seller's P&L: the aged-inventory surcharge and the low-inventory-level fee.
Individually, neither change sounds dramatic. Amazon itself describes the overall fulfillment fee increase as averaging "$0.08 per unit sold, or less than 0.5% of an average item's selling price." But averages hide the sellers who get hit hardest — and 2026's changes were specifically designed to squeeze two behaviors: holding inventory too long, and running it down too far. If your business does either, the real cost lands well above that headline 0.5%.
The Big Picture: What Actually Changed
Amazon gave sellers at least 90 days' notice before the new fee schedule took effect in January 2026. Three things moved:
- The aged-inventory surcharge now starts 90 days earlier. Extra storage charges used to kick in around the 271-day mark. In 2026, they begin at 181 days — six months, not nine.
- A new top tier was added for inventory over a year old, with a distinct, steeper rate for stock that's been sitting 12–15 months and an even steeper one beyond 15 months (455+ days). This is the change that catches long-tail and seasonal sellers off guard, because it applies even to SKUs that eventually do sell — they just sat too long first.
- The low-inventory-level fee threshold moved from 28 days of forecasted supply to 35 days, and for many sellers it's now calculated at the individual variation (FNSKU) level rather than blended across a parent ASIN. A best-selling color or size can trigger the fee even while the rest of the listing looks adequately stocked.
Referral fee percentages were left unchanged. This is a fulfillment- and storage-side squeeze, not a category-commission one.
The Aged-Inventory Surcharge: Six Months Is the New Nine
The core design hasn't changed — Amazon still charges the greater of a per-unit or a per-cubic-foot rate, calculated off a mid-month inventory snapshot, and it still escalates the longer a unit sits. What changed is how early the clock starts and how steep the final bands get.
The practical shift: inventory that used to have roughly nine months of "storage grace period" before extra surcharges applied now has six. And once a unit crosses into the 12-month range, the rate steps up again, with 2026 introducing an explicit ceiling tier for anything past 15 months that's noticeably higher than the 12-month band beneath it. (Amazon revises the exact per-band dollar figures periodically — always confirm the current numbers in your own Seller Central fee schedule rather than a fixed table, since third-party guides can lag a rate update by weeks.)
Why it matters more than it looks: aged-inventory fees compound with the storage fees you're already paying. A slow-moving SKU doesn't just cost you monthly storage — past day 180 it costs storage plus an escalating surcharge, and that surcharge roughly doubles or more at each subsequent tier. Sellers who used to treat "eventually it'll sell" as an acceptable inventory strategy are now paying real money to wait.
What to do about it
- Run an inventory-age report monthly, not quarterly. Amazon's own inventory dashboard flags units by age band — the earlier you see something approaching 180 days, the more pricing and promotional levers you still have.
- Price down or bundle before day 180, not after. A modest discount at 150 days is almost always cheaper than the surcharge at 200 days.
- Use removal or disposal orders deliberately. For genuinely dead stock, the cost of shipping it back or destroying it is frequently lower than a year of compounding surcharges.
- Rethink purchase order sizing. If you're ordering based on last year's velocity rather than trailing 90-day sell-through, you're manufacturing your own aged inventory.
The Low-Inventory-Level Fee: Now It Punishes Running Lean, Too
This is the fee most sellers don't see coming, because it charges you for the opposite problem — not having enough stock. Amazon introduced the low-inventory-level fee to discourage sellers from relying on Amazon's fulfillment network as just-in-time warehousing for high-velocity products. If your forecasted days-of-supply for a fast-moving SKU drops too low, Amazon assesses a per-unit fee on that item until inventory is replenished.
Two changes make this fee bite harder in 2026:
- The threshold rose from 28 to 35 days of forecasted supply. Sellers who comfortably cleared the old bar now need a wider safety margin to avoid the fee — effectively, Amazon is asking sellers to carry roughly a week more inventory than before.
- Enforcement increasingly happens at the FNSKU (individual variation) level, not the parent listing. A multi-variation listing where the medium and large sizes are well-stocked but the small size is nearly out can now trigger the fee on that one variation, even though the parent ASIN looks healthy in aggregate.
For sellers running lean on cash flow — a common and often sensible strategy for small operators — this creates a real tension: carry more safety stock and tie up working capital, or run lean and eat a per-unit fee on your best sellers. Some sellers report the fee eroding a noticeable share of revenue on individual high-velocity SKUs when reorder timing slips even briefly.
What to do about it
- Set reorder points at 35+ days of supply for FBA-forecasted items, not the 28-day cushion that used to be safe.
- Check variation-level inventory, not just parent-level. A dashboard showing "healthy" stock at the listing level can mask a starving variation.
- Shorten your replenishment lead time where possible, or negotiate better lead-time visibility with suppliers so reorders land before the threshold trips.
- Consider a hybrid fulfillment approach — keeping a portion of fast-moving SKUs in FBM or a 3PL as a buffer against FBA stockout fees while Amazon inventory catches up.
Doing the Math on Your Own Business
The averages Amazon publishes are a poor guide to what you'll actually pay, because the fee changes are specifically shaped around edge behavior — slow sellers and lean operators — not the median SKU. A useful exercise:
- Pull your inventory-age report and flag every unit currently past 150 days. That's your near-term aged-inventory exposure.
- Pull your top 10 SKUs by velocity and check current days-of-supply against the 35-day threshold. That's your low-inventory exposure.
- Multiply exposed units by the current per-unit or per-cubic-foot rate from your Seller Central fee schedule, not a third-party estimate.
Sellers who skip this exercise tend to discover the cost only after it shows up as an unexplained dip in a monthly settlement report — by which point a quarter's worth of fees has already accrued.
A Worked Example: Two SKUs, Two Failure Modes
It helps to see how these fees actually land, because the aged-inventory surcharge and the low-inventory fee punish opposite behaviors on the same seller's catalog.
SKU A — a seasonal home-goods item. A seller ordered a full year of stock ahead of a holiday push, sold through the first wave, and left the remainder sitting in a fulfillment center for the off-season. Under the old schedule, that remainder had until roughly month nine before extra storage charges applied. Under the 2026 schedule, the surcharge starts at month six, and by the time the seller notices the line item in a settlement report, several months of escalating fees have already accrued on units that were always going to sell eventually — just slower than the new clock allows for.
SKU B — a fast-moving supplement. The same seller runs a bestselling SKU tight to preserve cash flow, reordering only when Amazon's dashboard shows the parent listing adequately stocked. But one flavor variation sells faster than the others and quietly drops below 35 days of forecasted supply while the parent listing still looks "in stock." Because enforcement now happens at the FNSKU level, that single variation starts accruing a per-unit fee — on the exact SKU generating the most revenue.
Neither seller did anything reckless. Both were following inventory habits that were perfectly safe under the pre-2026 schedule. That's the real lesson: fee structure changes don't just raise costs, they can silently invalidate purchasing and replenishment habits that used to be sound, and the only way to catch that in time is to monitor age and days-of-supply at the SKU (or variation) level on a recurring cadence — not just glance at the parent-listing summary.
Why This Belongs in Your Books, Not Just Your Seller Dashboard
Amazon's settlement reports bundle referral fees, fulfillment fees, storage fees, and now these surcharges into a single deduction against your payout. That's convenient for cash flow visibility and terrible for understanding why your margin moved. If aged-inventory surcharges and low-inventory fees aren't broken out as their own expense lines in your books, they quietly blend into "cost of goods sold" or "selling fees" — and a genuine operational problem (inventory that's poorly timed in both directions) looks like a generic fee increase you can't do anything about.
Tracking these as distinct accounts — separate from your baseline referral and fulfillment fees — turns a vague sense that "Amazon fees went up" into an actionable signal: which SKUs are aging out, which are running dry, and whether your purchasing decisions are actually the root cause. Plain-text, version-controlled bookkeeping makes this kind of drill-down straightforward, because every transaction is a queryable line rather than a number buried inside a platform's opaque settlement PDF.
Keep Your Margins Visible as Fee Structures Shift
Marketplace fee schedules will keep changing, and the sellers who adapt fastest are the ones who can actually see where their money is going. Beancount.io offers plain-text accounting that gives you full transparency into every fee, surcharge, and settlement line — no black boxes, no vendor lock-in, and dashboards through Fava if you want the numbers visualized instead of just queried. Get started for free and keep your books as sharp as your inventory forecasting.
