Natural polymers — HTS 3913
Natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms
Chapter 39 › Heading 3913
2026 HTS Rev 19 Synced Rules verified Operational
Written to help non-specialists understand this page. Rates, dates, and legal facts come from the official records above and on the linked source.
HTS heading 3913 is a broad product category for certain natural polymers and chemically modified natural polymers presented in “primary forms.” Natural polymers include materials such as alginic acid; modified natural polymers can include hardened proteins and chemical derivatives of natural rubber. The phrase “not elsewhere specified or included” means the product does not belong in a more specific heading elsewhere in the tariff.
To reach the correct 8-digit HTS code, first confirm that the product belongs in heading 3913 and is in a primary form, such as a material supplied for further processing rather than a finished article. The subheading structure generally narrows the classification by the polymer’s material or type. Review the product’s chemical identity, formulation, physical form, and manufacturing process, then compare those facts with the official HTS wording and any applicable legal notes.
What to check
- Identify the exact natural polymer or modified natural polymer, including its chemical name and composition.
- Confirm that the goods are in a qualifying primary form, not a finished product or article made from the material.
- Check whether another HTS heading describes the product more specifically before using heading 3913.
- Read the complete 8-digit subheading descriptions and any section, chapter, or heading notes that limit their scope.
- Keep technical documentation—such as a specification sheet, safety data sheet, and manufacturing description—and ask a customs broker or request a binding ruling if the material or modification is difficult to classify.
HTS heading 3913 summary
Natural polymers is a 4-digit product category containing 1 published product-code lines in this snapshot. A heading does not carry one universal duty rate; classification must be narrowed to the line matching the product facts.
How to find your code in this category
A heading is a product category. To get the exact duty, narrow from this 4-digit heading to a sub-category (usually by material), then open the 8-digit code that matches your product.
Open any code in the tables below to see its exact duty rate, a duty calculator (enter your shipment value → estimated duty and landed cost), the rate-change history chart, and the country-by-country breakdown (including Section 301/232 add-on duties).
Why you have to click in: a single category can contain products with very different duties. The rate depends on the specific product — its material and construction — and on the country of origin, and those only get pinned down at the 8-digit code level. That is why this page points you to codes instead of showing one rate for the whole category.
Sub-categories
| Code | Description |
|---|---|
| 3913.90 | Other |
Product codes & duty rates
👇 Each row is a specific product code — click a blue code to open its full page with exact duty rates by country, the rate-history chart, and a duty calculator. 👉
| Code | Description | General (MFN) | Special | Column 2 |
|---|---|---|---|---|
| 3913.10.00.00 👉 | Alginic acid, its salts and esters | 4.2% | Free | 25% |
"Special" shows the free-trade-agreement rate; open a code to see exactly which countries qualify.
Common questions
What products fall under HTS heading 3913?
Natural polymers (for example, alginic acid) and modified natural polymers (for example, hardened proteins, chemical derivatives of natural rubber), not elsewhere specified or included, in primary forms. To classify a specific item you must pick the matching sub-category and 8-digit code above; the right choice usually depends on the material and construction of the product.
How do I choose the right code within this category?
Start from the sub-categories (typically divided by material—for example cotton versus man-made fibers), then open the active 8- or 10-digit code that matches the product. When unsure, a licensed customs broker or a CBP binding ruling can confirm the classification.
Reference information only, not customs, legal, or classification advice. Confirm the current code and rate against the official HTS before you import.