Confirm the Korean 10-digit HS code before the import declaration
Use the HS code from the foreign seller only as a reference, and in the import declaration use the 10-digit HS code the importer found in the Korean tariff schedule. If a wrong HS code leads to underreported tax, the importer pays the shortfall and the penalty tax.
Do not take only the HS code from the seller; also get photos and manuals that show the material and use of the goods.
Why the seller's HS code differs from the Korean HSK
The first 6 digits of an HS code are shared by the contracting parties to the HS Convention, and each country sets the remaining digits on its own. Korea files import declarations with a 10-digit code (HSK) that adds 4 digits after the first 6.
A seller usually gives the HS code used in the exporting country's declaration. Even when the 6 digits match, look up the last 4 digits again in the Korean tariff schedule.
Some goods are classified differently from the 6th digit. For sets made up of several goods and for parts of machines, the seller's HS code and the Korean HSK often differ.
When the HS code changes, not only the tariff rate but also import requirements such as KC certification and food inspection may change. Import requirements are looked up by HS code (Checking import requirements).
Tax the importer pays when the HS code is wrong
To import goods, a person must declare "the name, specifications, quantity and price of the goods" to the head of customs (Customs Act, Article 241 (1)) and file a tax return with the import declaration (Article 38 (1)). Even if the seller's HS code was used as given, the importer pays the shortfall.
If the declared tax is short, the importer files an amended return and pays the customs duty by the day after the date of the amended return (Article 38-3 (1)).
When the shortfall is paid after an amended return or a correction by the head of customs, the importer also pays a penalty tax of 10/100 of the shortfall plus an amount equivalent to interest for the period of late payment (Article 42 (1)).
Conversely, if too much tax was paid, the importer may apply to the head of customs for a correction within 5 years from the date of the first tax return (Article 38-3 (2)).
Advance ruling on tariff classification when the classification is unclear
A person who intends to import or export goods, the manufacturer of goods to be exported, a Licensed Customs Broker, and others may apply to the Commissioner of the Korea Customs Service, before filing the import or export declaration, for an advance review of the tariff classification of the goods (Article 86 (1)).
When goods identical to goods covered by a notified advance ruling are declared, the head of customs "shall apply the tariff classification in accordance with the notice" (Article 86 (5)). The ruling remains valid until the tariff classification changes (Article 86 (7)), so if you will keep importing identical goods, apply before the first import.
Source: Customs Act, Article 38 (Declaration and payment), Article 38-3 (Amendment and correction), Article 42 (Penalty tax), Article 86 (Advance ruling on the tariff classification to be applied to specific goods), Article 241 (Declaration of export, import or return). Based on the laws in force as of October 31, 2026.