If you’re an importer, you know you pay duties when goods enter the United States. But do you know exactly how those duties are calculated? Most importers rely on their customs broker to handle the math — and that’s fine in normal times. But these aren’t normal times. With the Supreme Court striking down IEEPA tariffs and billions in refunds now available, understanding how your duties were calculated is the first step toward understanding what you’re owed.
The duty calculation formula looks simple on the surface: Duty = Customs Value x Duty Rate. But each variable in that formula has layers of complexity. Let’s unpack them.
The Three Pillars of Duty Calculation
Every import duty assessment rests on three questions:
- What is the product? (Classification)
- What is it worth? (Valuation)
- What rate applies? (Rate determination)
Get any one of these wrong, and the duty amount is wrong. For IEEPA refund purposes, all three matter — because the IEEPA surcharge was an additional rate applied on top of the normal duty, calculated against the same customs value.
Pillar 1: Classification
Classification means assigning an HTS code to your product. The HTS code determines which rate line applies. A polyester jacket (HTS 6202.93) faces a different rate than a cotton jacket (HTS 6202.11). A stainless steel kitchen sink (HTS 7324.10) faces a different rate than a ceramic kitchen sink (HTS 6910.10).
Your customs broker assigns the HTS code when filing the entry summary. CBP can review and reclassify if they disagree. Classification disputes are one of the most common reasons for duty adjustments.
For a deep dive into how classification works and why it matters for IEEPA refunds, see our tariff classification explainer.
Pillar 2: Valuation
Customs valuation determines the dollar amount on which duties are calculated. For ad valorem duties (percentage-based), the customs value is the base. A 10% duty rate on a $100,000 shipment produces $10,000 in duties. The same rate on a $50,000 shipment produces $5,000.
The United States follows the WTO Agreement on Customs Valuation, which establishes a hierarchy of six valuation methods. In practice, the vast majority of imports use Method 1: transaction value.
Transaction Value is the price actually paid or payable for the goods when sold for export to the United States. In simpler terms, it’s what you paid your supplier, plus certain additions and minus certain deductions.
Additions to transaction value include:
- Packing costs paid by the buyer
- Selling commissions paid by the buyer
- Assists — materials, tools, dies, or engineering work you provided to the manufacturer for free or at reduced cost
- Royalties and license fees you’re required to pay as a condition of the sale
- Proceeds from any subsequent resale that accrue to the seller
Deductions from transaction value include:
- International freight and insurance from the exporting country to the U.S. (the U.S. uses FOB value, not CIF)
- Duties and taxes imposed in the United States
- Post-importation installation, assembly, or maintenance costs
This distinction between FOB and CIF is important. If your commercial invoice shows a CIF price (cost + insurance + freight), the international freight and insurance need to be deducted to arrive at the customs value. Many importers have entry summaries where the customs value differs from the invoice amount for this reason.
Pillar 3: Rate Determination
Once you know the product classification and customs value, the duty rate comes from the HTS. But “the rate” isn’t always a single number. Multiple rate layers can apply to the same product:
| Rate Layer | Source | Example |
|---|---|---|
| General (MFN) | HTS Column 1 General | 5.3% |
| Special | FTA or preference program | Free (under USMCA) |
| Section 301 | Trade Act of 1974 | 25% |
| Section 232 | Trade Expansion Act of 1962 | 25% (steel), 10% (aluminum) |
| IEEPA | Executive orders (now struck down) | 20%-145% |
| AD/CVD | Commerce Department determinations | Varies by product/company |
The total duty rate is the sum of all applicable layers. For a product subject to a 5.3% MFN rate, a 25% Section 301 rate, and a 20% IEEPA rate, the total was 50.3%. The IEEPA layer — 20% in this example — is what’s now refundable.
Doing the Math: A Step-by-Step Example
Let’s walk through a real-world duty calculation from start to finish.
Product: Stainless steel kitchen faucets from China Invoice value (CIF): $200,000 International freight and insurance: $12,000 HTS code: 8481.80.5090
Step 1: Determine Customs Value
Customs value = CIF price – international freight and insurance $200,000 – $12,000 = $188,000
(Assuming no assists, royalties, or other additions apply.)
Step 2: Look Up the Duty Rate
For HTS 8481.80.5090:
- General (MFN) duty rate: 2.0%
- Section 301 duty rate: 25.0% (China-origin goods under List 3)
- IEEPA duty rate: 20.0% (under EO 14259)
Step 3: Calculate Each Layer
| Layer | Rate | Customs Value | Duty Amount |
|---|---|---|---|
| MFN | 2.0% | $188,000 | $3,760 |
| Section 301 | 25.0% | $188,000 | $47,000 |
| IEEPA | 20.0% | $188,000 | $37,600 |
| Total | 47.0% | $88,360 |
Step 4: Identify the Refundable Amount
Only the IEEPA layer is refundable: $37,600
The MFN duty and Section 301 duty remain valid. Your IEEPA refund claim for this shipment is $37,600.
Now multiply that across dozens or hundreds of entries over 12+ months of importing, and you start to see why the total refund amounts for mid-size importers often reach six or seven figures.
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Valuation Pitfalls That Affect Your Refund
Since the IEEPA surcharge was calculated as a percentage of customs value, any error in your customs value directly affects your refund amount. Higher customs value means more IEEPA was paid and more is refundable. Lower customs value means less was paid and less is refundable.
Related-Party Transactions
If you buy from a related company (a subsidiary, parent, or affiliate), CBP may scrutinize your transaction value. Related-party pricing must be “arm’s length” — meaning comparable to what unrelated parties would pay. If CBP determines your related-party price was artificially low, they can adjust the customs value upward, which would increase your duty liability — but also increase the IEEPA amount paid and the refundable amount.
Assists
Assists are one of the most commonly overlooked additions to transaction value. If you provided your Chinese manufacturer with molds, tooling, engineering specs, or raw materials to produce your goods, the value of those assists should be added to the customs value. If they weren’t, your customs value (and duties paid) may be understated.
For IEEPA refund purposes, understated customs value means understated IEEPA payments — which means a smaller refund. However, correcting the valuation to add assists would also mean you owe more in non-IEEPA duties, so this cuts both ways.
First Sale Valuation
Some importers use “first sale” valuation — declaring the price in the first sale in a chain of transactions (manufacturer to middleman) rather than the last sale before import (middleman to importer). This is legal and can significantly reduce customs value, but it must be properly documented.
If your entries used first-sale valuation and the values were lower than they would otherwise be, your IEEPA payments were lower and your refunds will be correspondingly lower. This isn’t a problem — it just means your refund calculation needs to use the correct customs values.
How Different Duty Types Affect the Math
Not all duties are calculated the same way. Understanding the calculation method for each type matters when you’re trying to isolate the IEEPA component.
Ad Valorem Duties
Most duties — including IEEPA surcharges — are ad valorem, meaning they’re calculated as a percentage of customs value. The math is straightforward: rate x value = duty.
Specific Duties
Some duties are calculated per unit of quantity rather than as a percentage of value. For example, a specific duty might be $0.05 per kilogram or $2.50 per dozen. Specific duties are common for agricultural products, textiles, and some processed goods.
If your product is subject to a specific MFN duty but an ad valorem IEEPA surcharge, you’ll have two different calculation bases for the same entry — quantity for the MFN duty and value for the IEEPA duty. The entry summary will show both calculations separately.
Compound Duties
Compound duties combine ad valorem and specific components — for example, “3.5% + $0.15/kg.” These are relatively uncommon but add complexity to the calculation. Again, the IEEPA surcharge was always ad valorem, so the compound nature of the MFN duty doesn’t change the IEEPA calculation.
The Role of Your Customs Broker
Your customs broker handles the duty calculation on every entry. They classify the product, declare the customs value, apply the correct rates, calculate the duty, and transmit the entry summary to CBP through ACE (the Automated Commercial Environment).
The broker’s work product — the entry summary (CBP Form 7501) — is the primary document for your IEEPA refund claim. It shows:
- The HTS code for each product line
- The customs value for each line
- The duty rate for each layer (MFN, 301, IEEPA, etc.)
- The duty amount for each layer
- The HTS 9903 code indicating the IEEPA surcharge
If anything looks off — the customs value doesn’t match your invoice, the HTS code doesn’t match your product, or the IEEPA rate doesn’t match the executive order — flag it with your broker before filing your refund claim.
The Merchandise Processing Fee and Other Charges
Beyond duties, you also pay fees on imports. The main one is the Merchandise Processing Fee (MPF):
- Rate: 0.3464% of customs value
- Minimum: $31.67 per entry
- Maximum: $614.35 per entry
The MPF is not a duty — it’s a fee for CBP’s processing services. It’s not refundable under the IEEPA ruling.
Other charges you may see on your entry summary:
- Harbor Maintenance Fee (HMF): 0.125% of customs value for goods arriving by vessel
- Cotton fee: Small assessment on cotton imports
- Federal excise tax: On certain products (tobacco, alcohol, firearms)
None of these are IEEPA-related and none are refundable in this context. When calculating your IEEPA refund, make sure you’re isolating just the IEEPA duty amount — not the total charges on the entry.
How to Verify Your Duty Calculations
If you want to check whether the duties on your entries were calculated correctly, here’s a practical approach:
- Pull your entry summaries from ACE or request them from your broker
- Verify the customs value against your commercial invoices (remember to adjust from CIF to FOB if applicable)
- Look up the HTS code in the USITC database at hts.usitc.gov to confirm the correct rate
- Multiply customs value x rate for each duty layer and compare to the amount on the entry summary
- Sum the IEEPA amounts across all entries for your total refund estimate
For importers with hundreds of entries, this verification is best done systematically — either through your broker’s ACE reports or through a professional Impact Assessment that does the calculation for every entry.
The IEEPA tariff refund glossary defines all the technical terms in this article, and the guide to how U.S. import tariffs work provides broader context for how the duty system fits together.
Common Duty Calculation Errors That Affect IEEPA Refunds
Duty calculation errors are more common than most importers realize. Here are the ones that come up most frequently in the IEEPA refund context.
Incorrect Customs Value
If the customs value on your entry summary doesn’t match the actual transaction value (after proper adjustments for freight, assists, etc.), every duty calculation based on that value is wrong. For IEEPA refund purposes, an understated customs value means understated IEEPA payments and a smaller refund. An overstated customs value means you paid more IEEPA than you should have — and you’re owed more back.
Wrong Rate Applied
The IEEPA tariff rates varied by executive order and product category. If the wrong rate was applied to your entries — say 20% when it should have been 34%, or vice versa — your refund amount will be wrong. Cross-reference the rate on your entry summaries with the actual executive order rates using the HTS 9903 codes guide.
Missing IEEPA Codes
In some cases, IEEPA surcharges may have been assessed but the 9903 code wasn’t properly recorded on the entry summary. This is rare but not unheard of, especially during the early weeks of the IEEPA tariffs when brokers were scrambling to implement new filing requirements. If you know you paid IEEPA tariffs but don’t see 9903 codes on certain entries, your broker should investigate.
Double-Counting
Make sure you’re not double-counting duties when calculating your refund. Each entry summary is a distinct document covering a distinct set of goods. If the same shipment appears in your records more than once (due to amended entries, for example), use the most recent version.
Currency Conversion
If your commercial invoices are in a foreign currency, the customs value in U.S. dollars depends on the exchange rate used. CBP publishes official exchange rates for customs purposes, which may differ from market rates on the date of the transaction. Small exchange rate differences can compound across large shipments and multiple entries.
Why This Matters Now
Understanding how your duties were calculated isn’t just academic. It’s the foundation of your IEEPA refund claim. Every dollar of IEEPA duty you paid is a dollar you’re entitled to recover. But you need to know the exact amount — not an estimate, not a guess, but the actual IEEPA duty paid on every entry.
Your recovery path — whether it’s a Post-Summary Correction, a CBP protest, CIT litigation, or immediate capital — requires accurate duty calculations. The more precisely you can document what was paid and under which authority, the smoother the refund process goes.
If you import regularly and paid IEEPA tariffs on dozens or hundreds of entries, the total refund can be substantial. A mid-size importer paying $50,000 per month in IEEPA surcharges over 12 months would have $600,000 in refundable duties. Larger importers can be into the millions.
Request a free Impact Assessment to get an entry-by-entry calculation of your IEEPA tariff exposure. We’ll verify customs values, identify every IEEPA surcharge, and calculate your total refund amount across all recovery paths. The assessment is confidential, covered by mutual NDA, and delivered within 5-10 business days.
