9903.91.01 Explained: Section 301 China Four-Year Review, 25% Duty

Key Points

• HTS code 9903.91.01 imposes a 25% additional duty on articles the product of China, on top of the normal chapter 1-97 rate, for entries on or after September 27, 2024, as defined by U.S. note 31 to subchapter III of chapter 99.
• All 350 product-specific coverage windows under this code ran from September 27, 2024 through February 1, 2026; as of the facts date of October 11, 2026, every window has closed and zero subheadings remain actively covered.
• The covered products were overwhelmingly steel mill products, stainless and alloy steel forms, aluminum shapes, and selected base metals, drawn from the Section 301 four-year statutory review process under the 9903.91/.92 escalation series.
• Because all coverage windows ended on February 1, 2026, importers with entries dated between September 27, 2024 and February 1, 2026 should verify whether duties were correctly collected; entries after February 1, 2026 should not carry this code.
• Confirm current duty treatment for any affected subheading in the live HTSUS at hts.usitc.gov or with a licensed customs broker, as successor rates or codes may apply.

On this page

1. What 9903.91.01 is and what program created it
2. Covered products and HTS subheadings
3. The 25% rate and its effective window
4. How 9903.91.01 stacks with other duties on an entry
5. Current status: all coverage windows closed
6. What importers should do
7. Key references

HTS code 9903.91.01 is a Chapter 99 overlay code that added a 25% Section 301 additional duty on a defined set of Chinese-origin goods, effective for entries on or after September 27, 2024, under the four-year statutory review escalation of the Section 301 China tariff program. As of October 11, 2026, all 350 product coverage windows under this code ran only through February 1, 2026, meaning no subheadings are actively covered today. Importers with entries dated between September 27, 2024 and February 1, 2026 need to confirm that this code was reported and duties were collected correctly on those entries.

The links in this article go to the primary documents: the Federal Register notices, official tariff schedule pages, and CBP guidance themselves. Read the source.

What 9903.91.01 is and what program created it

Section 301 of the Trade Act of 1974, codified at 19 U.S.C. § 2411, authorizes the U.S. Trade Representative to impose additional duties on goods from countries engaged in unfair trade practices. The original Section 301 China actions, which created the familiar 9903.88 series codes, were launched in 2018 and covered four product lists.

The 9903.91 and 9903.92 series codes represent a separate, later escalation layer: the four-year statutory review of the original Section 301 China actions. That review process resulted in rate increases on selected subheadings across the existing lists. Code 9903.91.01 is one of the codes created through that review process to impose a 25% additional rate on specific Chinese-origin goods identified in U.S. note 31 to subchapter III of chapter 99 of the HTSUS.

The official heading text of 9903.91.01 reads: "Effective with respect to entries on or after September 27, 2024, articles the product of China, as provided for in subdivision (b) of U.S. note 31 to this subchapter." That note controls which chapter 1-97 subheadings fall under this code, and the coverage windows set the precise dates each subheading is subject to the extra duty.

Covered products and HTS subheadings

The facts block identifies 350 chapter 1-97 subheadings tied to 9903.91.01, all carrying the same effective window of September 27, 2024 through February 1, 2026. The product universe is concentrated in metals, particularly:

• Flat-rolled carbon and alloy steel (e.g. 7208, 7209, 7210, 7211, 7212, 7216, 7225, 7226 series subheadings)
• Stainless steel bars, wire, and strip (e.g. 7219, 7220, 7222, 7223 series)
• Other steel forms including tubes and structural shapes (e.g. 7222, 7305 series)
• Aluminum shapes, tubes, and plate (e.g. 7601, 7604, 7608, 7606 series)
• Ferroalloys and base metals (e.g. 7202, 8101, 8507, 2605, 8002 series)

A representative sample of the subheadings covered (all active September 27, 2024 through February 1, 2026) includes: 7212305000, 8101100000, 7211194500, 8507904000, 7222406000, 7305391000, 72254051, 72163300, 7210200000, 72091815, 7202934000, 72084060, 72112360, 72164000, 7226199000, 7210410000, 72259900, 72269125, 7206900000, 76069130, 72192100, 72221100, 72202070, 7217206000, 2605000000, 7210909000, 76082000, 7208540000, 72085100, 72191100, 72193500, 80012000, 7210690000, 76069230, 7226910500, 72230010, 72111975, 7604101000, 7601203000, and 76081000, among others. The full list of 350 subheadings is authoritative in U.S. note 31, subdivision (b), of the HTSUS. Confirm the complete list at hts.usitc.gov.

If you import metals, steel mill products, or aluminum from China and your goods fall in the 72xx, 73xx, 75xx, 76xx, 80xx, or select 85xx and 26xx chapters, the covered subheadings warrant a specific line-by-line check against note 31.

The 25% rate and its effective window

Rate

The HTSUS general column rate for 9903.91.01 is: the duty provided in the applicable subheading + 25%. That means the 25% is additive on top of the standard chapter 1-97 MFN (column 1 general) rate for the specific product. If a subheading normally carries a 3% MFN rate, an entry subject to 9903.91.01 would owe 3% + 25% = 28% total before any other overlapping duties are considered.

Effective window

Every subheading covered by 9903.91.01 carries exactly the same window: September 27, 2024 through February 1, 2026. Entries with a date of import before September 27, 2024 were not subject to this code. Entries with a date of import after February 1, 2026 are also not subject to this code under the coverage windows in the facts block. Only entries with dates of import falling on or between those two dates, for the specific subheadings listed, owed this 25% additional duty.

How 9903.91.01 stacks with other duties on an entry

Chapter 99 codes like 9903.91.01 are reported as a separate line on the entry summary alongside the chapter 1-97 classification line. They do not replace the underlying commodity code; they ride alongside it. This matters for stacking:

• Section 232 steel or aluminum duties (if applicable to the same product) may also apply. Whether Section 232 and Section 301 duties stack or interact for a specific product is governed by the applicable U.S. notes and CBP guidance. Confirm the stacking treatment with your broker and review the relevant CBP guidance at cbp.gov.
• Other Section 301 codes from the 9903.88 series may also cover the same subheading if prior List 1-4 duties apply. Review whether the underlying subheading already carried a 9903.88.xx overlay before September 27, 2024, and confirm which code governs after that date. See related coverage of the 9903.88 series in our articles on 9903.88.04 and 9903.88.09.
• Antidumping and countervailing duties (AD/CVD) on steel and aluminum from China are common and are assessed separately from Section 301 duties. They are not part of this code but can significantly affect the total duty bill on the same entry line.

When preparing or auditing entries that covered both an active Section 301 code and an active Section 232 code, consult the specific U.S. notes in chapter 99 for stacking rules. See the 2026 tariff code overview for broader context on how Chapter 99 codes interact.

Current status: all coverage windows closed

As of October 11, 2026 (the facts date for this article), all 350 product-specific coverage windows under 9903.91.01 ended on February 1, 2026. Zero subheadings remain in active coverage under this code. Entries dated after February 1, 2026 should not carry 9903.91.01.

This does not automatically mean the underlying goods are now duty-free or that Section 301 duties have disappeared. Other Section 301 codes in the 9903.88 or 9903.91/.92 series may continue to apply to the same subheadings. Confirm current duty treatment for any previously-covered subheading in the live HTSUS at hts.usitc.gov or with a licensed broker. Do not assume the rate reverted to pre-September 2024 levels without checking successor codes in U.S. note 31 and related notes.

Entries filed during the active window: audit posture

If your business imported Chinese-origin steel, aluminum, or base metal products between September 27, 2024 and February 1, 2026 under any of the 350 covered subheadings, confirm that 9903.91.01 was declared on the entry summary and that the 25% additional duty was collected. If it was omitted in error, a prior disclosure or amended entry may be appropriate. If it was assessed in error on an out-of-window or out-of-scope entry, a protest may be the vehicle for recovery. On protest timelines and Court of International Trade options, see our article on the 180-day road to the Court of International Trade.

What importers should do

• Audit entries from September 27, 2024 through February 1, 2026: For any entry covering a Chinese-origin good classified under one of the 350 subheadings in U.S. note 31(b), verify that 9903.91.01 was reported and the 25% additional duty was paid. Errors in either direction, underpayment or overpayment, should be corrected through the appropriate CBP mechanism.
• Stop applying this code to post-February 1, 2026 entries: All coverage windows closed on February 1, 2026. Entries dated after that date should not carry 9903.91.01 unless new authority is published reopening coverage, which is not reflected in the current facts.
• Check for successor codes on affected subheadings: The underlying goods may still face Section 301 duties under other 9903.88 or 9903.91/.92 codes. Verify current coverage in the live HTSUS at hts.usitc.gov and watch the Federal Register for any new notices from the U.S. Trade Representative.
• Review stacking with Section 232 and AD/CVD: Steel and aluminum imports from China frequently carry multiple simultaneous duties. Confirm the full duty stack for each affected subheading with a licensed customs broker before filing or amending entries.

Key references

• HTSUS at hts.usitc.gov: The official Harmonized Tariff Schedule of the United States, including chapter 99 and U.S. note 31 to subchapter III governing 9903.91.01 coverage.
• 19 U.S.C. § 2411 (Cornell LII): The statutory authority for Section 301 actions, including the four-year review process that produced the 9903.91 series.
• Federal Register (federalregister.gov): Search for USTR notices related to the Section 301 four-year review and rate escalations for the complete regulatory record behind 9903.91.01.
• CBP (cbp.gov): CBP guidance, CSMS messages, and entry instructions for reporting Chapter 99 Section 301 codes on ACE entry summaries.
• 9903.88.04 Explained: Section 301 China List 4, 25% Duty Rate: Background on the List 4 base-layer Section 301 code that may apply to overlapping subheadings.
• Protest Denied CIT: The 180-Day Road to Court of International Trade: Procedural guide for challenging duty assessments after a CBP protest is denied.