A higher FBA fulfillment fee can reduce a product’s profit on every subsequent sale. Before treating the difference as an overcharge, establish which fee changed, which rate applied to the shipment, and whether Amazon’s recorded measurements match the packaged product.
A useful fee audit produces a specific result: either the charge is explained, or you have a documented discrepancy to investigate with Amazon. It also tells you how much margin is affected and whether later orders show the expected fee after a correction.
This workflow is for existing products fulfilled by Amazon in the US. It focuses on the outbound FBA fulfillment fee. Monthly storage, inbound placement, low-inventory-level fees, referral fees and return-related charges need their own checks; combining them into one average makes the cause of a change harder to identify.
What an FBA fulfillment fee audit checks
An FBA fulfillment fee audit compares the fee actually charged on an eligible shipment with the fee expected under the applicable Amazon rules. The comparison needs the same marketplace, product configuration, rate period, category, price band, size tier and shipping-weight band.
A change from the previous fee is a useful signal. The previous fee is not automatically the correct benchmark for a later shipment. A seasonal rate, a different price band or a packaging change can legitimately produce a new charge.
Keep two numbers separate throughout the audit:
- Observed fee change per unit = new charged fee per unit − previous charged fee per unit
- Unexplained fee difference per unit = actual charged fee per unit − expected fee per unit for that shipment
The first finds candidates. The second estimates the discrepancy after you have checked the rules. Neither calculation, by itself, establishes reimbursement eligibility.
Step 1 Find a change worth investigating
In sellerboard, open Money Back → FBA Fee Changes and select the period you want to review. The page flags newer orders when it detects a different FBA fee for an ASIN. It shows the previous and new fees, the difference and an estimated overcharged amount. You can download the report in Excel or CSV. These are investigation leads; sellerboard’s documentation explicitly cautions that a fee change can be valid and that Amazon’s reimbursement decision can differ from the estimate. See the FBA Fee Changes guide.
Start with products where a small recurring difference could materially affect profit. A reasonable review priority is the unexplained difference per unit multiplied by the expected number of affected units. Until the difference has been validated, treat that as potential exposure rather than recoverable money.
Use sellerboard’s product-level profit analysis to understand the commercial impact. Filter the Profit Dashboard to the affected ASIN and marketplace, select comparable periods around the change, and expand the cost breakdown. Review fulfillment costs alongside net profit per unit. Use the dashboard or reports for the outcome; the quick profit-per-unit view on sellerboard’s Products page is an estimate. A fee investigation is more urgent when the increase materially changes profit per unit, even if the dollar amount looks small beside total account revenue.
Create a working file with these fields: marketplace and currency; child ASIN; SKU and FNSKU where relevant; example order or shipment identifier; shipment date; fee-charge date and applicable claim deadline; charged units; actual fulfillment fee; expected fee; reason for any difference; evidence; case status; and verification status. Exported report layouts can vary, so add the audit calculations yourself rather than assuming every column is already present.
Step 2 Compare the same product and the same fee
Choose a few affected shipments and a small comparison set. Confirm that they refer to the same sellable configuration. A single unit and a multipack, two variations, or packaging from different production runs may have different fee-relevant measurements.
Then verify the actual charge in Seller Central. In Payments, open the relevant transaction and its fee details. Depending on the Seller Central interface, this may appear as Transaction View or Manage Transaction. The transaction total includes more than fulfillment fees. Amazon’s transaction guidance describes the transaction-level reporting route. Keep the evidence tied to an identifiable order or shipment, rather than relying only on a dashboard average.
Normalize quantities carefully. If an order line contains two units and its fulfillment charge is $11.10, the corresponding fee is $5.55 per unit. Use the units associated with that charge. Do not divide by net units after returns or cancellations, and do not combine a refund adjustment or reimbursement credit with the original outbound fee.
Recent orders can still contain estimates or incomplete fee information. Verify that the charge you are comparing has been posted, and revisit incomplete records when Amazon’s data is available. A calculator result or fee preview is an estimate, not evidence of what was charged.
If several unrelated ASINs changed at the same time, check a shared rate or surcharge change before investigating each product’s dimensions. If only one configuration changed, its classification and measurements deserve closer attention. This comparison is a diagnostic aid, not proof of either explanation.
Step 3 Reconstruct the legitimate fee for that shipment
Use Amazon’s current US fulfillment-fee guidance and the schedule that applied when the shipment left the fulfillment center. The order date alone can put a shipment in the wrong rate period.
Check the applicable product type, price band, size tier and shipping-weight band. The US 2026 schedule distinguishes standard-size price bands below $10, $10–$50 inclusive and above $50. It also includes separate peak and non-peak schedules and a fuel and logistics surcharge. Check applicable discounts and additional charges, including Ships in Product Packaging (SIPP), Bulky packaging fees and Overmax handling. Amazon lists these in its 2026 fee summary. Compare the same fee components on both sides. Use the correct table and its notes together; a displayed base fee may exclude an applicable surcharge.
Record what changed between the comparison shipments. Examples include a change in the applicable price band, a peak-rate transition, different product classification or a revised packaged weight. Confirm the price Amazon used to determine the band; do not assume the customer’s net payment after a coupon is that price. Calculate the expected fee using the applicable rules, without adding a surcharge twice if your source already includes it.
Amazon’s fee-estimation tools help with this reconstruction. The Revenue Calculator lets you inspect inputs for a product, while Fee Preview provides estimates for FBA inventory. Save the relevant inputs and report version used in your audit. A current estimate cannot, on its own, prove what an older shipment should have cost.
Step 4 Check the packaged measurements and shipping weight
Download Fee Preview from Reports → Fulfillment → Payments in Seller Central. Amazon’s report specification includes package dimensions, weight, measurement units and size or weight classification, although headers can differ between versions. Compare those recorded attributes with the product in the packaging actually sent to FBA. Measure the complete sellable unit, including packaging and components shipped together, and keep the measurement units consistent.
Follow the size-tier and shipping-weight rules applicable to that product. Unit weight is the fully packaged scale weight. For the US rules, dimensional weight is packaged volume in cubic inches divided by 139, subject to Amazon’s tier-specific measurement rules. Small Standard and Extra-Large 150+ lb use unit weight; the other current tiers use the greater of unit or dimensional weight. Check Amazon’s size-tier definitions and dimensional-weight rules, including applicable minimum dimensions. Do not apply a universal rounding-to-the-next-pound rule.
A useful measurement check answers four questions:
- Does Amazon’s record describe the same packaged configuration that you inspected?
- Does the recorded measurement put the product in a different size tier or shipping-weight band?
- Would your verified measurement actually change the applicable fee?
- Was that packaging used on the shipments being investigated?
The third question prevents low-value disputes. A measurement can differ without changing the fee. Conversely, a small difference near a tier boundary can have a recurring cost impact.
Photograph the packaged unit and the measurement method, record the measurements, and note any packaging revision. Measurements from a newly reduced package do not establish that older shipments were overcharged. If Amazon’s measurements appear wrong, use its remeasurement process to investigate; a seller’s own measurement does not automatically replace Amazon’s record.
Step 5 Calculate the unexplained difference and its profit impact
Calculate each affected shipment or group of genuinely comparable shipments separately. Different rate periods or product configurations may need different expected fees.
Potential fee discrepancy = sum of (actual fee per unit − expected fee per unit) × affected units
Review both positive and negative differences rather than automatically offsetting one product’s possible overcharge against another product’s lower fee. Keep refunds, reimbursements and later adjustments in a separate reconciliation so they do not obscure the original charge.
A worked example
The following figures are hypothetical, already include the applicable charges for each scenario, and are not Amazon’s published rate table.
A product previously incurred a $5.40 fulfillment fee per unit. A later group of 600 units is charged $5.85 per unit. The seller verifies that a legitimate rate change makes the expected fee $5.55 for those shipments.
| Calculation | Result |
|---|---|
| Observed increase | $5.85 − $5.40 = $0.45 per unit |
| Increase explained by the applicable rate | $5.55 − $5.40 = $0.15 per unit |
| Remaining difference to investigate | $5.85 − $5.55 = $0.30 per unit |
| Potential discrepancy across 600 units | $0.30 × 600 = $180 |
Simply multiplying the full $0.45 increase by 600 would suggest $270. That would include $90 explained by the legitimate rate change. The audit prevents an overstated case.
Suppose the product sells for $30 and would earn $6.00 net profit per unit at the expected fee, with all other costs unchanged. The additional $0.30 lowers profit to $5.70 and net margin from 20% to 19%. At 2,400 comparable units a month, the continuing effect would be $720 a month.
That $720 is a forward-looking sensitivity estimate. The $180 is a historical discrepancy under review. Neither is an approved reimbursement, and neither should be booked as money recovered.
Step 6 Submit a focused investigation with supporting evidence
A useful case identifies the product, the affected transactions and the precise mismatch. Include the marketplace, ASIN and relevant SKU or FNSKU, example orders, shipment dates, quantities, charged fees, applicable rate basis and the evidence for a different measurement or classification.
Explain the requested action. You may need Amazon to confirm the recorded measurements, remeasure an eligible unit, explain a charge or review an eligible fee reimbursement. Keep those requests tied to the evidence. A list of changing fees is less useful than a worked comparison showing why the new charge appears inconsistent with the applicable rules.
Amazon’s US weight-and-dimensions reimbursement policy requires requests within 90 days of the fee charge and reimbursement depends on Amazon confirming inaccurate measurements. Search for “remeasure” in Seller Central to find the relevant tool. The policy also lists availability and request limits, including whether units are available to measure, whether the product has already been remeasured twice in 60 days and the account’s monthly request limit. Check the live policy before filing. Submit one request per FNSKU with the relevant evidence rather than a separate request for every order. Amazon declines duplicate claims for the same fee charge. A reporting tool’s historical lookback does not extend the claim window.
sellerboard’s FBA Fee Changes page provides a support-message template under Contact Seller Support. Adapt it to the validated discrepancy and attach the relevant evidence. The seller submits the case in Seller Central; sellerboard does not contact Amazon on the seller’s behalf.
If Amazon rejects the request, compare its explanation with the audit. A valid rate change means the expected cost should be updated. If the response leaves a specific measurement or transaction mismatch unresolved, address that point with additional evidence. Repeatedly submitting the same unsupported claim does not improve the analysis.
Step 7 Verify future charges and reconcile historical recovery
Keep two follow-up checks separate.
First, verify the fee on later comparable shipments after a confirmed correction. Check posted charges rather than relying only on an updated product measurement or a lower calculator estimate. Record the first verified shipment using the expected fee and review more than one order, particularly if different packaging versions remain in inventory.
Second, reconcile any historical reimbursement against the transactions reviewed. Record the amount requested, approved and actually credited, together with later adjustments or reversals. A corrected ongoing fee does not prove that past charges were reimbursed, and a reimbursement credit does not prove that future fees are correct.
Return to the product’s profit view to check the continuing effect on profit per unit. For a spreadsheet comparison, open Profit → Reports → Dashboard by Product in sellerboard and select the relevant period. Enable the detailed breakdown of Amazon fees, refund costs and COGS when you need individual fee components. The Reports guide notes that detailed columns can differ between periods, so align columns by their labels before comparing files. Keep cost definitions and periods consistent: advertising, price, refunds, storage and COGS changes can mask a fulfillment-fee correction.
Update the expected fee in pricing and replenishment decisions only after you have established the relevant cost basis. Keep an unresolved or provisional fee assumption visible so a product does not appear more profitable than the evidence supports.
A repeatable fee audit checklist
- Review fee-change candidates and prioritize their potential effect on profit
- Confirm the exact product configuration, marketplace, currency and charged units
- Retrieve posted transaction fees and retain the supporting records
- Check the applicable rate period, price band, category, size tier and shipping weight
- Separate explained changes from remaining differences
- Submit evidence through the current Amazon process within its applicable limits
- Verify subsequent charges and reconcile historical credits separately
A regular review of new exceptions is usually more useful than repeatedly rebuilding the entire catalogue’s fee history. Also check after packaging changes, a material rate change or an unexplained movement in profit per unit.
Common mistakes that weaken a fee audit
Treating the previous fee as the correct fee forever. Rebuild the expected charge for the shipment being reviewed.
Treating a lower Revenue Calculator result as a refund entitlement. Estimates, posted charges and reimbursement eligibility answer different questions.
Pooling variations or packaging versions. A shared parent listing does not establish identical measurements or fees.
Using ordered units, net units after returns or account-wide sales as the denominator. Match the quantity to the charge.
Assuming an updated measurement resolves everything. Verify subsequent actual charges and any separate historical credit.
Counting estimated recovery as current profit. Keep the disputed amount separate until the outcome is established and reconcile credits consistently.
Frequently asked questions
Does every FBA fee increase mean Amazon made an error
No. Rates, price bands, classification, weight or packaging can change legitimately. A fee-change report identifies records to review. The audit determines what remains unexplained after those factors are checked.
Can I audit an ASIN using only the Revenue Calculator
The calculator helps reconstruct an estimate, but an audit also needs the actual transaction charge and the inputs that applied to the shipment. A current calculator result cannot establish a historical overcharge on its own.
What is the difference between size tier and shipping weight
Size tier classifies the packaged product under Amazon’s measurement rules. Shipping weight is the weight basis used within the relevant fee calculation. Dimensional-weight rules and exceptions mean that the two checks must be performed separately.
Does sellerboard automatically prove or recover a fee overcharge
It flags changes for review and supports case preparation. You submit the evidence; Amazon determines whether a reimbursement is due.
How do I know the audit is finished
For a valid charge, document the explanation and update your cost assumptions. For a confirmed error, verify the fee on subsequent comparable shipments and separately reconcile the result of the historical claim. A support response alone may leave one of those tasks open.
Conclusion
A useful FBA fee audit connects a changed charge to its cause, its financial impact and a verifiable outcome. Start with the transaction, reconstruct the applicable fee, and investigate the remaining difference. Then check that the result is reflected in later charges and in the product’s profitability. That gives an existing seller a reliable basis for deciding whether to open a case, update pricing or revise a replenishment decision.
