Korea e-Tax Invoices: Hometax and API Guide

In Korea, every corporation and every individual business whose supplies reached KRW 80 million in the previous year must issue VAT tax invoices electronically and send them to the National Tax Service (NTS) by the day after issue. There are four legal routes: the NTS's own Hometax system, a registered issuance provider (ASP), an ERP system registered with the NTS, or other NTS-designated devices. For a foreign company's Korean entity, the usual way to automate this is to connect its billing or ERP system to a registered provider's API. This guide explains the rules from the statute text and how the integration is built.

Not tax advice. This article summarises the Value-Added Tax Act and its Enforcement Decree as we read them in October 2026. Have a Korean tax accountant confirm how the rules apply to your entity before you design your process around them.

What is a Korean e-tax invoice?

A tax invoice (세금계산서) is the VAT document a Korean business issues when it supplies goods or services to another business. Article 32 of the Value-Added Tax Act lists the core items it must carry:

1. The supplier's business registration number and name.
2. The buyer's registration number (or another identifier if the buyer is not a registered business).
3. The supply value and the VAT amount.
4. The date it was prepared.
5. Other items set by Presidential Decree.

An electronic tax invoice (전자세금계산서) is the same document issued through an electronic method set by the Decree, which passes through an authentication system that confirms who issued it and that it has not been altered. The buyer uses it to claim input VAT, so a late or wrong invoice is a problem for your customer as well as for you.

Who has to issue electronic tax invoices?

For foreign companies, the entity matters. A Korean subsidiary is a Korean corporation, so it falls under the corporate rule from its first sale. A Korean branch that is registered for VAT is generally in the same position, but confirm its status with your accountant. A foreign company that sells apps, games, cloud services or advertising to Korean consumers without a Korean place of business usually registers under the simplified regime in Article 53-2 instead; that regime is built around consumer sales, so ask your adviser whether any invoicing duty applies to your specific transactions.

When must an invoice be issued and sent to the NTS?

Three timing rules shape the system design:

• Issue at the time of supply. Article 34(1) of the VAT Act ties the invoice to the time the goods or services are supplied.
• Monthly invoices are allowed. Article 34(3) lets a business total a customer's supplies for a calendar month (or a shorter period it chooses within the month) and issue one invoice dated the last day, by the 10th of the following month. If the 10th is a weekend or public holiday, the deadline moves to the next business day.
• Send to the NTS by the next day. Decree Article 68(7) sets the deadline for transmitting the issued invoice to the NTS as the day after the issue date.

Late issuance and late transmission carry additional tax under the VAT Act. The amounts change from time to time, so check the current text with your accountant rather than relying on a figure in a blog post.

If an invoice was wrong, you do not edit it. Article 32(7) provides for an amended tax invoice (수정세금계산서), and your system needs a way to issue one that refers to the original.

What are the ways to issue an e-tax invoice?

Article 68(5) of the Enforcement Decree lists four methods:

Article 68(6) requires anyone who builds and runs the ERP, provider or device systems to register in advance with the NTS or the competent tax office. That is why most small and mid-sized companies do not connect directly: building and registering your own issuing system is a large project, while a registered provider has already done it.

Is there a Hometax API?

Hometax is a web service for taxpayers. For automated issuing from your own code, the practical route is a registered issuance provider's API or an ERP package that already has the registration. Providers differ in their API style, document formats, pricing per invoice, English documentation and support. Compare them on those points and on how they handle amended invoices and failed transmissions, not on marketing pages.

Hometax remains useful alongside an integration: your accountant can log in to see what the NTS has received, which is the final check that your system and the provider are in step.

How do you connect e-tax invoices to your billing or ERP system?

A clean integration has five parts:

1. Customer master data. Store each business customer's registration number, legal name, representative name, address and the email that receives invoices. Validate registration numbers when the customer is created. The NTS publishes a free status-check API on the public data portal that confirms whether a registration number exists and whether the business is active, suspended or closed.
2. A clear trigger. Decide what creates an invoice: a delivered order, a monthly usage total, a signed milestone. Write the rule down with your accountant, because it follows the supply-time rules above.
3. The provider call. Your system sends the invoice data to the provider's API, which issues it, delivers it to the buyer and transmits it to the NTS. Save the provider's response, including the identifier or approval number it returns, against your own invoice record.
4. Status tracking. Transmission can fail or be delayed. Poll or receive callbacks for each invoice's status and alert someone if an invoice is not confirmed within a day, so the next-day transmission deadline is not missed silently.
5. Amendments and cancellations. Build the amended-invoice flow from the start: refunds, price changes and returns all end up there.

The same records then feed your VAT reconciliation. If your ERP is the source of truth for sales, the invoice status should live in the ERP too, not only in the provider's dashboard. For how this fits a wider system, see ERP for foreign companies in Korea.

Can a finance team work in English?

The invoice that goes to the NTS uses the standard fields the law and the NTS format define. What your team sees does not have to be Korean. A common pattern for foreign-owned entities:

• The internal billing screens, approval steps and reports are in English for head office and in Korean for local staff, with the same data underneath.
• Item descriptions on the invoice are written so the Korean buyer recognises them; many companies use Korean or bilingual descriptions.
• The provider integration maps your English field names to the provider's format, so nobody needs to work in the provider's Korean dashboard day to day.

This is also where an English-language internal tool is most useful. If head office needs to approve invoices above a certain amount, the approval can live in your system, with only the approved invoices passed to the provider.

Who decides what?

As a development studio we build the last row and help with the paperwork and communication on the Korean side, but the tax treatment is your accountant's call and the provider contract is signed by your company.

What does an integration cost?

In our pricing catalogue (version 1.1, 23 September 2026), a simple one-way API integration is KRW 0.3M–0.6M and a two-way data sync KRW 0.8M–1.5M, excluding VAT. An invoicing integration with status tracking and amendments usually sits in the two-way range. Provider fees per invoice are separate and are paid to the provider. If the invoicing is part of a new internal system, see custom ERP development cost in Korea.

Frequently asked questions

Do foreign companies have to issue e-tax invoices in Korea?

A Korean subsidiary does, because every corporation must issue electronically under Article 32(2) of the VAT Act. A VAT-registered branch is generally in the same position. A foreign company selling electronic services to Korean consumers under simplified registration falls under a separate regime. Confirm your entity's position with a Korean tax accountant.

Can I issue tax invoices in English?

The invoice data follows the standard fields set by Korean law and the NTS format, and the buyer is a Korean business, so descriptions are usually written in Korean or both languages. Your internal billing screens, approvals and reports can be fully in English.

How do I connect Hometax to our system?

Most companies do not connect to Hometax directly. They connect their billing or ERP system to an issuance provider registered with the NTS, which issues the invoice and transmits it. Hometax is then used to check what the NTS has received.

What is the deadline for sending an e-tax invoice to the NTS?

The day after the issue date, under Article 68(7) of the VAT Enforcement Decree. Monthly consolidated invoices may be issued by the 10th of the following month under Article 34(3) of the VAT Act.

How do I check a Korean business registration number?

Use the NTS business registration status service, available as a free API on Korea's public data portal. It confirms whether a number is registered and whether the business is active, suspended or closed.

Sources

All checked October 2026.

• Korea Ministry of Government Legislation, Value-Added Tax Act (Articles 32, 34 and 53-2)
• Korea Ministry of Government Legislation, Enforcement Decree of the Value-Added Tax Act (Article 68)
• National Tax Service, Hometax
• National Tax Service, English site
• Public Data Portal, NTS business registration verification and status API

Automating invoicing for your Korean entity?

If your Korean entity needs invoices issued from your own billing or ERP system, with English screens for head office, send us your project details. See what we build on the software development in Korea page, and how invoicing fits a wider launch on the Korea market entry page. Consultations, meetings and documents are handled in English by our founder.