An Amazon FBA fee overcharge is the sneakiest kind of margin leak. Nothing goes missing. No inventory gets damaged. Your dashboard looks normal. But somewhere in a fulfillment center, a machine measured your product wrong — and now every single unit you sell pays a fulfillment fee for a size tier it doesn't belong in.
Unlike a lost shipment, nobody notifies you. The fee just changes — sometimes by a few cents, sometimes by a dollar or more — and it keeps getting charged until you notice. In our experience auditing seller accounts, mis-measured dimensions are one of the most common discrepancies we find, and one of the easiest to fix once you know where to look.
- Amazon re-measures products with automated Cubiscan machines. A damaged unit, changed packaging, or wrong item on the scanner can silently push your ASIN into a higher size tier or weight band.
- Compare Amazon's billed dimensions (FBA fee preview / fulfillment fee data in Seller Central) against your own tape-measure numbers for every top ASIN.
- One inch — or one ounce — can jump a size tier. A small per-unit overcharge compounds fast: $0.45 × 900 units/month is roughly $4,860 a year on a single ASIN (illustrative).
- Fix it in two moves: request a re-measurement (corrects fees going forward), then file an FBA fee dispute for past overcharges — which historically reach back only about 90 days.
- Because the lookback is short, monthly fee audits beat annual ones. Anything you don't catch within roughly a quarter is usually unrecoverable.
How Cubiscan measurement errors happen (and why they stick)
Amazon doesn't take your word for your product's size. Fulfillment centers run items across Cubiscan machines — automated sensors that capture length, width, height, and weight in seconds. Those numbers feed directly into the fee engine that prices every pick, pack, and ship for that ASIN.
The machine is fast, not smart. It measures whatever lands on it, in whatever condition it arrives. That's where errors creep in:
- Routine re-measurement events. Amazon periodically re-scans catalog items. If the unit pulled for scanning is atypical — a puffed-up poly bag, a box that absorbed humidity, a corner crushed in transit — the inflated reading becomes your official dimensions.
- Packaging changes. You switch suppliers or shrink your box, but Amazon keeps billing the old, larger dimensions until a new scan happens. It also cuts the other way: a scan taken during a temporary oversized-packaging run can stick long after you fix it.
- Damaged or deformed units. A single dented master carton or a mangled retail box can get scanned as the reference unit. Your product didn't change; the sample did.
- The wrong unit measured entirely. Multipacks scanned with dunnage attached, a bundle measured as its largest component, or a case pack confused with a sellable unit. We've seen billed dimensions that don't match any physical configuration the seller ships.
Here's the part that costs real money: a wrong measurement persists silently. There's no alert, no line item that says "your fee went up because we re-measured." The new fee simply applies to the next order and every order after it. Most sellers only look at fees when they set up a listing, which means a bad scan in March can quietly tax every unit through Q4 — right through your highest-volume months.
How to spot an Amazon FBA fee overcharge: billed vs. actual dimensions
Finding an overcharge is a comparison exercise: what Amazon thinks your product measures versus what it actually measures. You need both numbers.
Step one: pull what Amazon is billing you
In Seller Central, two places show Amazon's on-file numbers per ASIN:
- FBA fee preview (Fee Preview report). Found under fulfillment reports, this lists each ASIN's product dimensions, weight, size tier, and estimated fulfillment fee — exactly what the fee engine is using right now.
- Fulfillment fee / transaction reports. These show the fees actually charged per order. Useful for catching the date a fee changed, which usually marks the re-measurement event.
Step two: measure the real thing
Take a sellable unit — packaged exactly as it ships to Amazon — and measure it with a tape measure and a decent scale. Longest side, median side, shortest side, and unit weight. Round the way Amazon does (dimensions are generally rounded, and billing uses the greater of unit weight or dimensional weight for larger items — check the current rules in Seller Central for your category).
Step three: check the size tier
Amazon prices fulfillment by size tier, and tiers are cliff-edged. The US tiers run roughly like this (approximate boundaries — always confirm against Amazon's current size tier chart in Seller Central):
| Size tier | Rough boundary (US, approximate) | What typically lands here |
|---|---|---|
| Small standard | Up to ~15" × 12" × 0.75", up to ~1 lb | Flat, light items: cards, thin apparel, accessories |
| Large standard | Up to ~18" × 14" × 8", up to ~20 lb | Most everyday products; fees step up by weight band |
| Large bulky | Beyond large standard, up to ~50 lb | Small furniture, bulk goods, big boxed items |
| Extra-large | Oversize and/or very heavy, multiple sub-tiers | Furniture, equipment — fees jump substantially |
Notice how tight those boundaries are. A product that truly measures 0.7" thick belongs in small standard; a Cubiscan that reads a slightly bowed mailer at 0.9" pushes it into large standard. An 18.2" reading on a 17.8" box does the same at the next boundary. Within large standard, weight bands mean a few recorded ounces can also bump the fee. One inch — sometimes one ounce — is a tier jump, and every unit pays the difference.
Sort your fee preview data by units sold and check your top movers first. Flag any ASIN where (a) the billed dimensions differ from your measured dimensions by more than rounding, or (b) the billed size tier is higher than the tier your own numbers produce. A 0.2" discrepancy that stays inside the same tier costs you nothing; a 0.2" discrepancy that crosses a boundary costs you on every order.
The compounding math: small per-unit overcharges, big annual losses
The reason an FBA fee overcharge deserves a monthly check is velocity. The error isn't a one-time event like a lost carton — it's a per-unit tax.
Worked example (illustrative): say a Cubiscan reads your mailer a half-inch too tall and your ASIN jumps a tier, adding $0.45 per unit. You sell 900 units a month. That's $405/month — and if nobody catches it for a year, $0.45 × 900 × 12 = $4,860 gone from one ASIN. Here's the same overcharge across different sales velocities:
| Units / month | Overcharge / unit | Monthly loss | 12-month loss | Recoverable at ~90-day lookback |
|---|---|---|---|---|
| 100 | $0.45 | $45 | $540 | ~$135 |
| 300 | $0.45 | $135 | $1,620 | ~$405 |
| 900 | $0.45 | $405 | $4,860 | ~$1,215 |
| 2,000 | $0.45 | $900 | $10,800 | ~$2,700 |
| 5,000 | $0.45 | $2,250 | $27,000 | ~$6,750 |
All figures illustrative. Read the last column carefully: if the error ran for a full year but fee-error claims only reach back roughly 90 days, the seller doing 900 units a month recovers about $1,215 of a $4,860 loss. The other ~$3,600 is simply gone. That gap — between what leaked and what's still claimable — is the whole argument for auditing monthly instead of annually. It's the same math that drives every category in our breakdown of what Amazon typically owes sellers: industry audits consistently find 1–3% of revenue leaking to unclaimed discrepancies, and fee overcharges are a steady contributor.
How to request a re-measurement and file an FBA fee dispute
Once your tape measure disagrees with Amazon's numbers, the fix has two parts: correct the dimensions going forward, then claw back what you already overpaid. Both are standard, policy-compliant Seller Central processes — no gray areas, no account risk. Here's the sequence we use:
Measure and photograph your packaged unit
Measure a sellable unit exactly as it ships — packaging included — with a tape measure visible in the photos. Capture length, width, and height each against the tape, plus the unit on a scale showing weight. Clear evidence up front is what separates a quick correction from a case ping-pong.
Open a case requesting a re-measurement
In Seller Central, open a support case (Help → FBA → issue with fees/dimensions) asking Amazon to re-measure the ASIN. Include your photos and measured numbers. Amazon pulls a unit at a fulfillment center and re-scans it — a Cubiscan check, but this time with your evidence on record. If the re-measure confirms your numbers, the size tier and fee are corrected from that point forward.
Dispute the past fees
The re-measurement fixes the future; it does not automatically refund the past. Once the corrected dimensions are on file, file an FBA fee dispute for the orders charged at the wrong tier. Reference the case ID from the re-measurement, the date the fee changed (from your fulfillment fee reports), and the per-unit difference. Note the clock: fee-error claims have historically been limited to roughly 90 days of past charges — confirm the current window in Seller Central before you assume anything older is claimable.
Verify the reimbursement actually lands
Watch your Reimbursements report and match the credit against your own count of overcharged orders. Partial payouts are common — Amazon may credit some orders and not others. If the math doesn't reconcile, reply on the case with your order-level numbers. Every reimbursement should match a specific discrepancy; unmatched gaps are money still on the table.
A successful re-measurement only fixes fees going forward. Disputes for past overcharges historically reach back only about 90 days — and Amazon has been shrinking claim windows across the board, as we covered in our breakdown of the 60-day reimbursement deadlines. If a bad scan happened ten months ago, most of that money is unrecoverable no matter how good your evidence is. The only defense is catching errors fast: an annual audit finds a year of leakage but recovers a quarter of it. A monthly audit finds errors while nearly all of the loss is still claimable.
One honesty note, because it matters: re-measurement cuts both ways. If Amazon's on-file dimensions are somehow smaller than your true packaged size, a re-scan will raise your fee. That's not a reason to avoid audits — billing accuracy protects you at scale — but it is a reason to measure carefully yourself before you open the case.
Fee overcharges are one leak of eight — audit them together
Fee overcharges rarely travel alone. The same account that has two mis-cubed ASINs usually also has lost inbound units, returns that never made it back to stock, and warehouse-damaged inventory that was never reimbursed. Amazon says it proactively reimburses many of these, but automation misses units, pays partial amounts, and uses its own valuations — the details are in our plain-English guide to Amazon's reimbursement policy.
You can absolutely run the fee check in this post by hand — and you should, at least for your top ASINs. But doing it every month, across your whole catalog, alongside the other seven discrepancy categories, is where DIY stops scaling. (We ran the honest numbers on that trade-off in DIY vs. software vs. agency.)
ClawbackPro's free scan includes fee overcharges as one of its eight recovery categories. It compares your billed dimensions and fees at the unit level — not summary level — flags ASINs where the numbers don't reconcile, and files compliant cases with the evidence attached. Pricing is 15% of what's actually recovered, charged only after Amazon pays. If nothing's wrong with your fees, you pay nothing and you've confirmed your biggest ASINs are billed correctly. Either outcome beats not knowing.
FBA fee overcharge FAQ
How do I know if Amazon is overcharging my FBA fees?
Pull the dimensions and weight Amazon has on file per ASIN from the FBA fee preview / fulfillment fee reports in Seller Central, then measure a packaged unit yourself with a tape measure and scale. If Amazon's numbers put the item in a higher size tier or weight band than your measurements do, you're likely paying an Amazon FBA fee overcharge on every unit that ships.
How far back can I dispute an Amazon FBA fee overcharge?
Fee-error claims have historically been limited to roughly 90 days of past fees, and Amazon's claim windows have generally been shrinking — so treat 90 days as the practical ceiling and confirm the current policy in Seller Central. A re-measurement corrects fees going forward, but overcharges older than the lookback are usually gone for good. That's the core argument for monthly audits over annual ones.
What is a Cubiscan and why does it get my dimensions wrong?
A Cubiscan is the automated measuring machine Amazon uses in its fulfillment centers to capture length, width, height, and weight. It measures whatever is placed on it — so a popped poly bag, a bent box corner, attached dunnage, or a multipack measured as a single unit can record inflated dimensions that then drive every fulfillment fee for that ASIN until someone requests a re-measure.
Can requesting a re-measurement backfire on me?
A re-measurement request is a standard, policy-compliant process with no account risk. The honest caveat: it cuts both ways. If Amazon's on-file numbers were actually lower than your true packaged dimensions, a re-scan can raise your fee. Measure your packaged unit carefully first, and only request a re-measure when your own numbers show you're being over-billed.