9903.91.06 Explained: Section 301 China Four-Year Review, 25% Duty

Key Points

• HTS 9903.91.06 imposes an additional 25% duty on articles that are the product of China, as provided for in subdivision (g) of U.S. note 31 to subchapter III of Chapter 99, effective for entries on or after January 1, 2026.
• The five subheadings covered under this code (85051100, 85076000, 2504105000, 2504900000, and 2504101000) were all in scope only from January 1, 2026 through February 1, 2026; as of the facts date of October 13, 2026, none remain in force.
• Because no subheadings are currently active under 9903.91.06, importers bringing in these goods today should confirm their correct Chapter 99 treatment with the current HTSUS or a broker before filing.
• When 9903.91.06 was in force, it stacked on top of the regular Chapter 1-97 duty, meaning the total rate was: the normal column 1 general rate plus 25%.
• Entries made during the January 1 to February 1, 2026 window that were classified incorrectly may be subject to post-summary correction or protest; verify your entry summaries for that period.

On this page

1. What 9903.91.06 is and the program behind it
2. Affected products and HTS coverage
3. Rate and how it stacks with other duties
4. Effective window and current status
5. How this code appears on a CBP entry
6. Interaction with other Section 301 provisions
7. What importers should do
8. Key references

HTS 9903.91.06 is a Chapter 99 Section 301 tariff code that adds 25% to the normal duty rate on specific Chinese-origin goods covered by subdivision (g) of U.S. note 31 to subchapter III of Chapter 99. It became effective for entries on or after January 1, 2026. All five product subheadings that were placed under this code ran only through February 1, 2026, so as of October 13, 2026, no subheadings are currently active under 9903.91.06. Importers and brokers who made entries during that narrow window need to confirm those entries were classified and duty-assessed correctly.

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

What 9903.91.06 is and the program behind it

9903.91.06 sits within the Section 301 China tariff structure, which uses Chapter 99 codes in the 9903.88 and 9903.91 series to impose additional duties on Chinese-origin goods. The 9903.88 codes cover the original Section 301 Lists 1 through 4. The 9903.91 and 9903.92 series represent a separate tier: escalations arising from the four-year statutory review of those original Section 301 measures.

9903.91.06 specifically implements subdivision (g) of U.S. note 31 to subchapter III of Chapter 99 of the HTSUS. That note defines which subheadings fall under this code and the conditions of coverage. The official heading text for 9903.91.06 reads: "Effective with respect to entries on or after January 1, 2026, articles the product of China, as provided for in subdivision (g) of U.S. note 31 to this subchapter."

For context on closely related four-year-review codes at other rate levels, see our articles on 9903.91.01, 9903.91.02, 9903.91.03, and 9903.91.04.

Affected products and HTS coverage

U.S. note 31(g) placed five Chapter 1-97 subheadings under 9903.91.06. All five shared the same effective window: January 1, 2026 through February 1, 2026. They are:

• 8505.11.00 - permanent magnets of metal and articles thereof (check current HTSUS for full description)
• 8507.60.00 - lithium-ion accumulators (batteries)
• 2504.10.5000 - natural graphite (crystalline flake, a specific form)
• 2504.90.0000 - natural graphite, other
• 2504.10.1000 - natural graphite (another crystalline form)

These are Chinese-origin goods only. Country of origin determines applicability; goods of other countries are not covered by 9903.91.06 regardless of where they enter the United States. Confirm exact product descriptions against the HTSUS for each subheading, as descriptions above are for orientation only.

As of October 13, 2026, all five subheadings have exited the scope of 9903.91.06. The facts block confirms 0 subheadings are in force under this code today.

Rate and how it stacks with other duties

When 9903.91.06 was in force, the HTSUS general column rate was: the duty provided in the applicable subheading + 25%.

That means the 25% is an additional duty layered on top of, not instead of, the normal column 1 general rate for each underlying subheading. For example, if subheading 8507.60.00 carried a 3.4% column 1 general rate, an entry subject to 9903.91.06 would owe 3.4% plus 25%, for a combined rate of 28.4%, before any other applicable Chapter 99 overlays.

Importers should also verify whether the underlying subheadings were simultaneously subject to any 9903.88 series codes (the original Section 301 list rates). When multiple Chapter 99 codes apply, each additional rate stacks. Confirm exact stacking treatment with a licensed customs broker, or check the current HTSUS for any applicable notes limiting double-counting.

Effective window and current status

9903.91.06 became effective for entries on or after January 1, 2026. All five product subheadings were in scope from January 1, 2026 through February 1, 2026.

As of October 13, 2026 (the as-of date of these facts), every subheading that was placed under 9903.91.06 has ended its coverage window. The code itself remains in the HTSUS with its heading text intact, but no goods are currently being classified under it because no active subdivision (g) subheadings remain.

Importers should not apply 9903.91.06 to current shipments without first verifying with the live HTSUS and any current CBP guidance that a product has been re-listed under the code. The absence of active subheadings is a material fact for current classification decisions.

How this code appears on a CBP entry

9903.91.06 is a Chapter 99 overlay code. On a CBP entry summary (CBP Form 7501), it does not replace the underlying Chapter 1-97 subheading. Instead, it appears as a second line alongside the primary classification. A correctly filed entry for an affected good during the January 1 to February 1, 2026 window would show:

• Line 1: The Chapter 1-97 subheading (for example, 8507.60.0000), with its normal column 1 general rate applied to the dutiable value.
• Line 2: 9903.91.06, with the 25% additional duty applied to the same dutiable value.

Both lines reference the same commercial invoice value for the Chinese-origin goods on that shipment line. If you want to check whether your broker calculated duty correctly on entries filed during that window, see our guide on how to check whether your broker calculated the duty correctly.

Interaction with other Section 301 provisions

The four-year-review codes (9903.91 series) exist alongside, not instead of, the original Section 301 list codes in the 9903.88 series. For products that were simultaneously covered by a 9903.88 code and 9903.91.06, both additional duties applied. The 9903.91.06 rate of 25% does not subsume or offset any pre-existing 9903.88 rate on the same subheading.

Related Section 301 codes you may need to consider for goods in similar product categories include 9903.88.15 (List 4A, 7.5%) and 9903.88.16 (List 4B, suspended). Whether any of those apply to your specific subheadings requires checking the current HTSUS and U.S. note 20 (which governs Lists 1-4) alongside U.S. note 31 (which governs the four-year-review escalations).

For a broader overview of how 2026 tariff codes interact, see our 2026 tariff code overview.

What importers should do

• Audit entries from January 1 to February 1, 2026: If you imported Chinese-origin goods under subheadings 85051100, 85076000, 2504105000, 2504900000, or 2504101000 during that window, confirm that 9903.91.06 was reported on each entry summary and that the 25% additional duty was assessed on the correct dutiable value. Miscalculated entries may be correctable via post-summary correction or protest.
• Do not apply 9903.91.06 to current shipments without verification: All five subheadings exited scope on February 1, 2026. Check the live HTSUS and current CBP guidance before adding this code to any new entry.
• Confirm stacking with other Chapter 99 codes: For any of the five subheadings, determine whether a 9903.88 series code also applied during the January to February 2026 window. Both rates would have been additive, and underpayment of either creates a duty liability.
• Monitor U.S. note 31 for future changes: The four-year-review process can result in additional products being added to or removed from subdivision (g) coverage. Bookmark hts.usitc.gov and watch for CBP CSMS messages announcing updates to Chapter 99 note 31 subheadings.

Key references

• Harmonized Tariff Schedule of the United States (HTSUS), hts.usitc.gov - The authoritative source for 9903.91.06 heading text, U.S. note 31(g), and all underlying subheading descriptions.
• U.S. Customs and Border Protection (CBP), cbp.gov - CBP guidance, CSMS messages, and entry filing instructions for Section 301 additional duties.
• Federal Register, federalregister.gov - Federal Register notices announcing Section 301 four-year-review rate changes and product list modifications.
• White House, whitehouse.gov - Presidential proclamations and executive orders governing Section 301 China tariff actions.
• 19 U.S.C. 2411 et seq. law.cornell.edu - The statutory authority for Section 301 trade actions.
• 9903.91.04 Explained: Section 301 China Four-Year Review, 25% Duty - Related four-year-review code at the same rate level.
• How Do I Check Whether My Broker Calculated the Duty Correctly? - Practical guide to auditing entry summaries for Section 301 duty accuracy.