Every imported product carries a stack, and the stack starts with the MFN rate, the most favoured nation duty for the product's HTS subheading. That is the base rate, and it is usually small, a few percent. On top of it sit the trade remedy layers: Section 301 duties on Chinese goods, which run from 7.5 to 100 percent across roughly 370 billion dollars of imports, and Section 232 duties on steel, aluminum, and copper at 50 percent, and autos at 25 percent.
Then come the fees. The merchandise processing fee is 0.3464 percent of the entered value, with a minimum of 33.58 dollars and a maximum of 651.50 dollars per entry, and the harbor maintenance fee is 0.125 percent on ocean freight. Neither is large on its own. Both are charged on every entry, and both are easy to forget when the remedy rates are the ones in the headline.
The arithmetic is the part people get wrong. The rates add, they never compound. A product with a 3.4 percent base rate, a 50 percent Section 232 duty, and a 25 percent Section 301 duty pays 78.4 percent. A calculator that compounds them, applying each rate to the total including the last, reaches a higher number, and that number is wrong. CBP adds the rates to the customs value, and the sum is the duty.
The reason this matters is that the compounded figure is the one that shows up in spreadsheets. A buyer who compounds a 50 and a 25 reaches a rate over 90 percent and kills a product line that would have survived at 78.4. The difference between the two numbers is the difference between a product that works and a product that does not, and the correct arithmetic is the one CBP uses.
Penn Wharton's budget model put the average effective tariff rate at 6.7 percent in July 2026, and that number gets quoted as if it described any given product. It does not. An average across all imports tells you nothing about your shipment, because the stack is product specific. A product with no remedy layer pays the base rate. A product with two remedy layers pays close to 80 percent. The average is the middle of a distribution, and your product sits somewhere in it.
The practical move is to build the stack for your own subheadings, line by line, and stop quoting the average. List the base rate, the 301 layer, the 232 layer, the MPF, and the HMF, and add them. That sheet is your rate. Everything else is commentary.
The stack is not fixed. A forced labor Section 301 action added 10 and 12.5 percent rates across 60 economies starting July 24, 2026, and it landed on products that had no remedy layer the month before. A brand that built its stack in June and did not rebuild it in August was underpaying its own cost model and did not know it.
Rebuild the stack whenever a notice publishes, and rebuild it per subheading, not per product line. Two products in the same line can sit in different subheadings with different remedy layers, and a single rate for the line hides the difference. The stack is a living document. Treat it like one, and the margin stops surprising you.
Keep reading: Section 232 Steel Tariffs: What Counts as Steel Content, Antidumping Duties: How Commerce Sets the Rate, How should DTC brands split tariff costs with suppliers?.
You add them, you never compound them. A product with a 3.4 percent base MFN rate, a 50 percent Section 232 duty, and a 25 percent Section 301 duty pays 78.4 percent. CBP adds the rates to the customs value, and the sum is the duty. Compounding them reaches a higher, wrong number.
Section 232 duties are 50 percent on steel, aluminum, and copper, and 25 percent on autos. Section 301 duties on Chinese goods run from 7.5 to 100 percent across roughly 370 billion dollars of imports. The rates change by proclamation, so check the current annex for your subheading.
The MPF is 0.3464 percent of the entered value, with a minimum of 33.58 dollars and a maximum of 651.50 dollars per entry. The harbor maintenance fee is 0.125 percent and applies to ocean freight only. Both are charged on top of the duty rates.
Penn Wharton's budget model put it at 6.7 percent in July 2026, but that is an average across all imports and it tells you nothing about your shipment. Your rate is the stack for your own subheadings: base rate plus each remedy layer plus the fees, added together.