# HS code 2901.23: Unsaturated, butene (butylene) and isomers thereof

> HS code 2901.23 covers unsaturated, butene (butylene) and isomers thereof. It sits in heading 29.01 (acyclic hydrocarbons) in chapter 29 (organic chemicals). Other goods of heading 29.01 are classified under 2901.10 (saturated), 2901.21 (unsaturated, ethylene), 2901.22 (unsaturated, propene (propylene)), 2901.24 (unsaturated, buta-1,3-diene or isoprene) and 1 other.

Source: https://staging.border.bot/hs-codes/290123
Last updated: 13 October 2026

[HS codes](https://staging.border.bot/hs-codes) / [Chapter 29](https://staging.border.bot/hs-codes/29) / [29.01](https://staging.border.bot/hs-codes/2901) / [2901.23](https://staging.border.bot/hs-codes/290123)

## Key facts

- HS code: 2901.23
- Covers: Unsaturated, butene (butylene) and isomers thereof
- Heading: [29.01: Acyclic hydrocarbons](https://staging.border.bot/hs-codes/2901)
- Chapter: [29: Organic chemicals](https://staging.border.bot/hs-codes/29)
- Edition: HS2022
- Duty rates: [Set by each country’s tariff](https://staging.border.bot/countries)

## What this code covers

HS code 2901.23 covers unsaturated, butene (butylene) and isomers thereof.

The legal text of the subheading is “Unsaturated: Butene (butylene) and isomers thereof”, read under “Unsaturated”, in HS2022.

## What it doesn’t cover

Other goods of heading 29.01 are classified under 2901.10 (saturated), 2901.21 (unsaturated, ethylene), 2901.22 (unsaturated, propene (propylene)), 2901.24 (unsaturated, buta-1,3-diene or isoprene) and 1 other.

- [2901.10](https://staging.border.bot/hs-codes/290110) Saturated
- [2901.21](https://staging.border.bot/hs-codes/290121) Unsaturated: Ethylene
- [2901.22](https://staging.border.bot/hs-codes/290122) Unsaturated: Propene (propylene)
- [2901.24](https://staging.border.bot/hs-codes/290124) Unsaturated: Buta-1,3-diene and isoprene
- [2901.29](https://staging.border.bot/hs-codes/290129) Unsaturated: Other

## How it is structured

2901.23 is a six-digit subheading. Its first two digits, 29, are the chapter; the first four, 2901, are heading 29.01; the last two, 23, identify the subheading within the heading.

Countries add their own digits after these six for their national tariff lines.

- Chapter 29: Organic chemicals
- Heading 29.01: Acyclic hydrocarbons
- Within the heading: Unsaturated
- Subheading 2901.23: Butene (butylene) and isomers thereof

## In other countries

No national tariff lines under 2901.23 are live on border.bot yet. Tariffs built on the Harmonized System (HS2022) use 2901.23 at six digits and add their own digits after it.

- Previous subheading: [2901.22](https://staging.border.bot/hs-codes/290122) Unsaturated: Propene (propylene)
- Next subheading: [2901.24](https://staging.border.bot/hs-codes/290124) Unsaturated: Buta-1,3-diene and isoprene

## Frequently asked questions

### What does HS code 2901.23 cover?

HS code 2901.23 covers unsaturated, butene (butylene) and isomers thereof.

### Which heading and chapter is HS code 2901.23 in?

HS code 2901.23 is in heading 29.01 (acyclic hydrocarbons) in chapter 29 (organic chemicals).

### Where are goods of heading 29.01 classified when 2901.23 doesn’t fit?

Other goods of heading 29.01 are classified under 2901.10 (saturated), 2901.21 (unsaturated, ethylene), 2901.22 (unsaturated, propene (propylene)), 2901.24 (unsaturated, buta-1,3-diene or isoprene) and 1 other.

## Sources and updates

The Harmonized System legal text comes from border.bot release 1 (edition HS 2022), imported from a file, and has been live since 13 October 2026.

This page was last updated on 13 October 2026.

Guidance from published tariff data, not a binding ruling. For a decision customs must follow, apply to the destination’s customs authority for a binding tariff ruling.

Machine-readable: https://staging.border.bot/hs-codes/290123.json