How US Import Duties Actually Stack
Most Amazon sellers think they pay one duty rate. The reality is more complicated: multiple tariff layers can stack on top of each other. For our reference 500ml stainless steel vacuum insulated flask from China, a 7.2% base rate became 19.7% in total duty (rates as of 24 July 2026). Here is how it works, in plain English.
See how duties stack
Take a 500ml stainless steel vacuum insulated flask imported from China at $10.00 FOB (Free On Board). Each duty layer is calculated on that FOB value and added to the others; no layer is charged on another layer.
Example: 500ml stainless steel vacuum insulated flask from China
HS 9617.00.10
Calculated by MarginStack, rates as of 24 July 2026
Effective duty rate
19.7%
Base cost before any duties
7.2% of $10.00 FOB value
12.5% of $10.00 FOB value
$1.97 in duties on a $10.00 product
The 8 duty authorities, explained
Tap any layer to see the full explanation, current rates, and who it applies to.
Applies to: Customs value, which is the FOB price alone. International freight and insurance are excluded from customs value by 19 CFR 152.103.
Rate
Set per tariff line in the schedule. It depends entirely on your product's HS code.
What is it?
The base US import duty for a tariff line, published in the Harmonized Tariff Schedule (HTS). It applies to goods from any country the US trades with normally.
How it works
Every other duty layer is charged on the same customs value, and some layers are capped by reference to this rate, so it is resolved first. When the schedule cannot be reached, or prints a rate per kilogram or per liter instead of a percentage, the calculator shows duty as unavailable rather than guessing.
Key fact
A different tariff code can carry a different base rate and a different set of layers. Getting the code right matters more than any other input.
What the calculator approximates
Rates charged per quantity (per kilogram, per liter, per dozen) are not converted. For those lines the calculator shows duty as unavailable.
Example
500ml stainless steel vacuum insulated flask
HS 9617.00.10
7.2%
As read from the USITC schedule on 13 September 2026, 9617.00.10 carries 7.2%, which on a $10.00 FOB value is $0.72 per unit.
Current status
In force. The calculator reads each rate live from the USITC tariff schedule when you calculate. The example on this card was read on 13 September 2026.
Sources
- USITC Harmonized Tariff Schedule
- 19 CFR 152.103, transaction value
Applies to: Covered steel, aluminium and copper articles and derivatives, from any origin.
Rate
Since 8 June 2026, tiered by annex under Proclamation 11032. The tiers are not modelled by the calculator.
What is it?
National security duties on steel, aluminium and copper, charged on the material a product is made of rather than on where it comes from.
How it works
Where a Section 232 duty applies to a tariff line, the Section 301 forced labour duty does not. Whether a given product is covered depends on its tariff line and the annexes, not on whether it happens to contain metal.
Key fact
Section 232 and the forced labour duty do not stack on the same line: the first switches the second off.
What the calculator approximates
The calculator applies a single rate per metal, matched by tariff chapter, and does not model the tiers, the annexes or the metal weight threshold. That overstates duty for some products. The single rate it uses has not yet been verified against the proclamation.
Current status
In force. Since 6 April 2026 the duty is charged on the full customs value of a covered article, under Proclamation 11021. Since 8 June 2026 the rate is set in tiers by annex, under Proclamation 11032 at 91 FR 34085.
Sources
- Proclamation 11021 (full customs value, from 6 April 2026)
- Proclamation 11032, 91 FR 34085 (tiers, from 8 June 2026)
Applies to: Chinese-origin goods whose tariff line is on one of the lists.
Rate
Depends on the list a product's tariff line is on. The calculator reads the lists from its Section 301 data file.
What is it?
Additional duties on Chinese-origin goods from the 2018 action, organised into lists that were rolled out between 2018 and 2019.
How it works
Some tariff lines carry a temporary exclusion that removes this duty until the exclusion expires. The calculator shows an active exclusion and what the duty would be without it.
Key fact
Being from China does not by itself mean a product is on a list. It depends on the tariff line.
What the calculator approximates
Exclusions are checked against today's date rather than the date a calculation is made for.
Example
500ml stainless steel vacuum insulated flask from China
HS 9617.00.10
Not on a list
As of 13 September 2026, 9617.00.10 is not on any 2018 list, so this layer is zero for the reference flask even though it comes from China.
Current status
In force. It stacks on top of the forced labour duty for Chinese goods on a list; it does not replace it.
Applies to: Goods from the 60 investigated economies, unless a suppression applies.
Rate
Since 24 July 2026: a flat 10.0% for 17 economies, a flat 12.5% for 38, capped net of MFN at a 10.0% ceiling for the European Union and Taiwan, and at a 12.5% ceiling for Japan, Korea and Switzerland.
What is it?
Additional duties on imports from 60 economies, imposed after investigations into forced labour, effective 12:01 a.m. eastern time on 24 July 2026.
How it works
Since 24 July 2026, the duty is charged on customs value. For the capped economies it tops the MFN rate up to the ceiling, so MFN plus this duty never exceed it. It does not apply where a Section 232 duty applies to the line, where goods of Canada or Mexico enter duty free under the United States-Mexico-Canada Agreement (USMCA), or where entry is properly claimed under a chapter 98 provision.
Key fact
Among the origins you can pick in the calculator, since 24 July 2026 the flat 10.0% group includes India, Mexico, Bangladesh, Indonesia, Canada, and the flat 12.5% group includes China, Vietnam, Thailand, Philippines.
What the calculator approximates
The calculator does not model the Annex I and Annex II product exemptions, so it overstates duty for exempted products. It does not model the in transit carve out for goods already on the water, which needs a loading date and an entry date. It does not ask whether an entry is claimed under chapter 98, so it never applies that exemption. It switches the duty off when a Section 232 duty is charged, which is close to but not exactly the notice's rule. For Canadian and Mexican goods it asks whether they qualify under USMCA, and when you are not sure it shows the duty both ways.
Example
500ml stainless steel vacuum insulated flask from China
HS 9617.00.10
12.5%
Since 24 July 2026, China is in the flat 12.5% group, so the reference flask pays $1.25 per unit on its $10.00 FOB value.
Current status
In force since 12:01 a.m. eastern time on 24 July 2026.
Applies to: Imports from all countries, between 24 February 2026 and 24 July 2026.
Rate
10.0% of customs value, between 24 February 2026 and 24 July 2026, under Proclamation 11012 at 91 FR 9339.
What is it?
A temporary surcharge on imports from all countries, in force between 24 February 2026 and 24 July 2026.
How it works
Between 24 February 2026 and 24 July 2026, the surcharge was 10.0% for its whole life. It no longer applies to goods entered after it expired.
Key fact
The calculator charges it only on a calculation dated inside its window, which is how a before and after comparison can show it.
Current status
Historical. It expired on 24 July 2026, when the Section 301 forced labour duty took effect.
Applies to: No imports since 20 February 2026.
Rate
None since 20 February 2026. Past rates are not stated here because they have not been traced to a primary source.
What is it?
Tariffs imposed under emergency economic powers.
How it works
The calculator keeps this layer only so a calculation dated before 20 February 2026 still resolves.
Key fact
Since 20 February 2026, no IEEPA duty applies to any import.
Current status
Historical. Struck down on 20 February 2026.
Sources
- Primary citation not yet traced
Applies to: Goods from Canada. The product scope is not stated here because it has not been verified.
Rate
Not stated here: the rate has not been verified against a primary source, and the calculator does not model it.
What is it?
Additional duties on goods from Canada.
How it works
For goods from Canada that do not qualify under USMCA, the duty the calculator shows is lower than what will be owed, because these duties are missing from it. For goods that qualify, it has not been established whether these duties apply.
Key fact
If you import from Canada, ask your customs broker what these duties add to your product.
What the calculator approximates
Not modelled at all.
Current status
In effect since 22 August 2026, and not included in the calculator.
Applies to: Only products covered by an order, from the countries the order names.
Rate
Set order by order. The calculator does not model these duties.
What is it?
Duties on a specific product from a specific country, and sometimes from a specific manufacturer, imposed after an investigation finds dumping or unfair subsidies.
How it works
Most products are not covered by an order. When one is, it can change whether a product is viable at all, so it is worth checking before you order.
Key fact
Ask your customs broker whether an order covers your product and supplier.
What the calculator approximates
Not modelled. The calculator never includes antidumping or countervailing duty.
Current status
Orders come and go case by case. The calculator does not check them.
Where the calculator approximates
Plainly, the things the calculator leaves out or simplifies today.
- MFN: Rates charged per quantity (per kilogram, per liter, per dozen) are not converted. For those lines the calculator shows duty as unavailable.
- Section 232: The calculator applies a single rate per metal, matched by tariff chapter, and does not model the tiers, the annexes or the metal weight threshold. That overstates duty for some products. The single rate it uses has not yet been verified against the proclamation.
- Section 301, China lists: Exclusions are checked against today's date rather than the date a calculation is made for.
- Section 301, forced labour: The calculator does not model the Annex I and Annex II product exemptions, so it overstates duty for exempted products. It does not model the in transit carve out for goods already on the water, which needs a loading date and an entry date. It does not ask whether an entry is claimed under chapter 98, so it never applies that exemption. It switches the duty off when a Section 232 duty is charged, which is close to but not exactly the notice's rule. For Canadian and Mexican goods it asks whether they qualify under USMCA, and when you are not sure it shows the duty both ways.
- Section 338: Not modelled at all.
- AD/CVD: Not modelled. The calculator never includes antidumping or countervailing duty.
Does this apply to me?
Answer a few quick questions to see which duty layers apply to your products, and which the calculator approximates.
Step 1 of 2
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Calculate My True MarginThis page is for informational and educational purposes only. Duty calculations are estimates. Final determination is made by US Customs and Border Protection (CBP). Consult a licensed customs broker for official classification. Tariff rates are subject to change without notice.