9903.91.03 Explained: Section 301 China Four-Year Review, 100% Duty

Key Points

• HTS code 9903.91.03 adds a 100% ad valorem duty on top of any otherwise-applicable rate for covered Chinese-origin goods, effective for entries on or after September 27, 2024.
• All 10 product subheadings that were covered under this code had an effective window of September 27, 2024 through February 1, 2026; as of the facts date of October 12, 2026, none of those subheadings remain in force under 9903.91.03.
• The covered goods were a specific set of Chinese-origin electric vehicles and certain medical-device syringes, governed by U.S. Note 31(d) to Subchapter III of Chapter 99.
• This code is part of the Section 301 four-year statutory review escalations housed in headings 9903.91 and 9903.92, separate from the original List 1-4 codes under 9903.88.
• Importers with entries from the September 27, 2024 through February 1, 2026 window should verify correct classification and duty payment, as post-summary corrections and protests may still be available depending on entry dates.

On this page

1. What 9903.91.03 is and who created it
2. Affected products and HTS coverage
3. Rate structure and stacking with other duties
4. Effective window and current status
5. Interaction with other Section 301 provisions
6. What importers should do
7. Key references

HTS code 9903.91.03 is a Chapter 99 overlay code that imposed an additional 100% ad valorem Section 301 duty on specific Chinese-origin electric vehicles and certain medical-device syringes. It applied to entries on or after September 27, 2024, and every product subheading under the code expired on February 1, 2026. As of October 12, 2026, no subheadings remain active under this code. Importers whose entries fell within that window need to confirm that duties were correctly assessed and that any correction or protest avenues are addressed promptly.

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

What 9903.91.03 is and who created it

9903.91.03 belongs to the Section 301 China tariff framework, specifically the escalation layer that emerged from the four-year statutory review of the original Section 301 measures. While the foundational List 1 through List 4 duties live under heading 9903.88 in Chapter 99 of the HTSUS, the four-year review produced a separate cluster of escalated rates housed under headings 9903.91 and 9903.92. Code 9903.91.03 is one node within that cluster.

The official heading text reads: "Except as provided in heading 9903.91.10, effective with respect to entries on or after September 27, 2024, articles the product of China, as provided for in subdivision (d) of U.S. note 31 to this subchapter." The operative legal authority is U.S. Note 31(d) to Subchapter III of Chapter 99 of the HTSUS. Confirm the full text of that note directly in the current HTSUS on the USITC website, as note text can be amended.

For background on how the original List codes work, see our articles on 9903.91.01 (the 25% four-year review code) and 9903.88.15 (List 4A at 7.5%).

Affected products and HTS coverage

U.S. Note 31(d) enumerated 10 specific Chapter 1-97 subheadings as the product scope for 9903.91.03. All 10 carried the same effective window: September 27, 2024 through February 1, 2026. The subheadings were:

• 9018.32.00.00 (syringes, with or without needles, for medical use)
• 8702.90.31.00 (motor vehicles for transport of 10 or more persons, spark-ignition)
• 8702.40.61.00 (motor vehicles for transport of 10 or more persons, electric)
• 8703.80.00 (passenger motor vehicles with electric motors, other)
• 9018.31.00 (syringes, needles, catheters, related items)
• 8703.70.00 (passenger vehicles, plug-in hybrid)
• 8703.60.00 (passenger vehicles, hybrid, non-plug-in)
• 8703.90.01.00 (other passenger motor vehicles)
• 8702.40.31.00 (buses, electric)
• 8702.90.61.00 (buses, spark-ignition, other)

Country of origin is determinative: only goods the product of China are subject to 9903.91.03. Goods from all other countries are unaffected by this code. If you are uncertain whether your goods qualify as product of China under the applicable substantial-transformation rules, confirm with a licensed customs broker.

What is not covered

Heading 9903.91.03 contains a carve-out: goods that fall under heading 9903.91.10 are excepted. Check the current HTSUS and any applicable product exclusions listed under 9903.91.10 to determine whether an exception applies to a specific entry. The facts block for this article is silent on the scope of 9903.91.10, so verify that detail directly in the HTSUS or with your broker.

Rate structure and stacking with other duties

The HTSUS general column rate for 9903.91.03 is stated as: "The duty provided in the applicable subheading + 100%." This means the 100% is layered on top of, not in place of, whatever duty otherwise applies to the Chapter 1-97 classification.

How stacking works on an entry

On a CBP entry, the Chapter 1-97 classification (for example, 8703.80.00) appears on one line with its normal column 1 general rate. The Chapter 99 code 9903.91.03 rides on a separate line referencing the same goods. CBP collects both. A vehicle that carries, say, a 2.5% normal duty rate would therefore face 102.5% in total ad valorem duty during the window this code was active.

Additional duties from other Chapter 99 provisions, such as Section 232 steel and aluminum tariffs if the vehicle contains those inputs at entry, would also stack. The facts block does not specify any interaction with such provisions, so confirm the full duty stack for your specific product with your broker or attorney.

Effective window and current status

Every product subheading covered by 9903.91.03 was effective from September 27, 2024 and ran through February 1, 2026. As of October 12, 2026, all 10 subheadings have expired under this code. Zero subheadings remain in force today.

This does not mean past liability disappears. Entries liquidated during the window with an incorrect duty assessment, or entries that are still unliquidated, remain subject to the 100% rate for the covered period. Importers should check the liquidation status of all relevant entries in ACE via CBP.gov.

If a product that was previously covered has since been reclassified or moved to a different Chapter 99 overlay code after February 1, 2026, that coverage would appear under a separate heading. Confirm current coverage in the live HTSUS, as the facts block is silent on post-February 1, 2026 treatment.

Interaction with other Section 301 provisions

9903.91.03 is an escalation code, not a replacement for the underlying List duties. Goods that were already subject to a 9903.88 series code (List 1, 2, 3, or 4) before September 27, 2024 may have continued to carry that List duty alongside or instead of 9903.91.03, depending on how U.S. Note 31 and the relevant subheadings interact. The facts block does not specify exactly which 9903.88 codes co-applied, so verify the complete duty stack against the full Chapter 99 schedule for each subheading.

For reference on how the List 4 baseline codes operate, see our articles on 9903.88.15 and 9903.88.04. The four-year review family also includes 9903.91.01 at a 25% escalation rate, covering a different set of products.

A general overview of the 2026 tariff code landscape is available at our 2026 tariff code overview.

What importers should do

• Audit entries from September 27, 2024 through February 1, 2026. Identify all Chinese-origin entries covering the 10 subheadings listed above and confirm that the 100% additional duty under 9903.91.03 was correctly reported and collected. Cross-reference entry summaries in ACE.
• Check liquidation status and protest deadlines. If an entry was liquidated with an incorrect duty amount, a protest must be filed within 180 days of the liquidation date. Entries still open may be corrected via post-summary correction. See our article on the protest-to-CIT timeline for procedural context.
• Verify current classification for ongoing shipments. Because no subheadings remain active under 9903.91.03 as of October 12, 2026, importers of the same goods should confirm what Chapter 99 codes, if any, apply to current entries by consulting the live HTSUS and CBP guidance.
• Review product exclusions under 9903.91.10. If your goods may qualify for the exception carved out by heading 9903.91.10, obtain the current exclusion list from the HTSUS and document the basis for any claimed exception before filing.

Key references

• Harmonized Tariff Schedule of the United States (USITC) - Official HTSUS including Chapter 99, heading 9903.91.03 and U.S. Note 31(d)
• U.S. Customs and Border Protection (CBP) - ACE entry management, CSMS messages, and Section 301 guidance
• Federal Register - Official notices implementing and modifying Section 301 four-year review escalations
• White House - Presidential proclamations relating to Section 301 China tariff actions
• 19 U.S.C. 2411 et seq. (Section 301 statutory authority), via Cornell LII - The Trade Act of 1974 provisions authorizing Section 301 actions