Chapter 99 of the Harmonized Tariff Schedule is where all the special tariff programs live — Section 232, Section 301, IEEPA reciprocal tariffs, and a host of other provisions. It's also where most of the confusion in U.S. importing happens.
If you've looked at your 7501 entry summary and seen codes starting with 9903, you've encountered Chapter 99. This reference guide maps the most common Chapter 99 codes to their programs, explains how they interact with your base classification, and highlights what to watch for.
What Chapter 99 Is
The HTSUS is organized into 99 chapters. Chapters 1 through 97 cover product classifications — everything from live animals (Chapter 1) to works of art (Chapter 97). Chapter 98 covers special import provisions. Chapter 99 is reserved for temporary modifications to tariff rates imposed by presidential proclamation or executive order.
When the president imposes additional tariffs — whether under Section 232, Section 301, IEEPA, or any other authority — those tariffs are implemented through Chapter 99 codes. These codes are added to your entry in addition to the base HTSUS classification. They don't replace the base code; they stack on top of it.
How Chapter 99 Codes Work
Your base classification determines what the product is and what the standard duty rate is. Chapter 99 codes determine whether additional tariffs apply.
For example, if you import a machine classified under 8422.40.0090 (packaging machinery) with a base duty rate of zero, the machine enters duty-free under normal circumstances. But if an IEEPA reciprocal tariff applies to that HTS code from the country of origin, a Chapter 99 code gets added — say, 9903.01.25 — and an additional duty is assessed on top of the zero base rate.
The critical point is that Chapter 99 applicability depends on the base HTS classification and the country of origin. If the classification is wrong, the Chapter 99 determination is unreliable. This is why classification comes first.
Common Chapter 99 Code Ranges
9903.80.01 through 9903.80.xx — Section 232 (Steel and Aluminum): These codes apply additional tariffs on steel (25%) and aluminum (10%) imports, plus derivative products. The scope is defined by HTS codes listed in the presidential proclamation. If your base classification is in Chapter 72, 73, or 76, or in the derivative product list, these codes may apply.
9903.88.01 through 9903.88.xx — Section 301 (China): These codes apply additional tariffs on goods from China at rates of 7.5% or 25%. The scope is defined by product lists (Lists 1 through 4B), each with its own set of covered HTS codes. Applicability depends on both the HTS code and the country of origin being China.
9903.01.01 through 9903.01.xx — IEEPA Reciprocal Tariffs: These codes apply the reciprocal tariffs imposed under IEEPA authority. Rates vary by country and have changed multiple times through executive orders. This is the program where most of the refund opportunities exist, because rates were imposed, paused, reduced, and modified repeatedly.
9903.85.xx — Section 232 Derivative Tariffs: These codes are a subset of Section 232 and apply to products that are derivative of steel or aluminum — meaning they contain steel or aluminum but are classified outside of Chapters 72, 73, and 76. This is the code range most commonly misapplied. A code like 9903.85.68 applies a derivative aluminum tariff, but only if the base HTS classification is on the derivative product list. Many products that contain aluminum are not on that list.
How They Stack
Multiple Chapter 99 codes can apply to the same entry line simultaneously. An import from China might owe the base duty, plus Section 301, plus IEEPA. An import of steel products might owe the base duty plus Section 232 plus IEEPA.
Each additional tariff is calculated on the customs value (the declared transaction value), not on top of the previous tariff. They're additive, not compounding. But they add up fast — a product with a 3% base rate, 25% Section 301 rate, and a 20% IEEPA rate would owe 48% total.
What to Watch For
Misapplied derivative codes. If you see 9903.85.xx on an entry for a finished machine or assembled product, verify that the base HTS classification is actually on the Section 232 derivative product list. Many are not.
Multiple Chapter 99 codes on the same line. This isn't automatically wrong — stacking is legitimate when all programs independently apply. But if one of them doesn't apply, the total duty is overstated.
Chapter 99 codes on duty-free products. A product with a zero base duty rate can still attract Chapter 99 tariffs. The zero base rate doesn't exempt it from 232, 301, or IEEPA — those are independent assessments.
Codes that have been modified. IEEPA codes in particular have been subject to multiple executive order changes. A code that applied a 25% rate in January may apply a 10% rate in March and no rate in May. The entry date determines which rate was in effect.
Using This Information
The next time you review a 7501, look at the Chapter 99 codes. Map each one to its program using the ranges above. Ask yourself: does this program actually apply to this product from this country? If you're not sure, that's worth investigating — because if the answer is no, you've been overpaying.