South Korea e-Tax Invoice (Hometax)

Key Features

Table and page extensions adding Korean business registration number (사업자등록번호) with checksum validation, sub-business (종사업장) code, and taxation type to customer, company information, and posted sales documents

Distinct handling of taxable 세금계산서 and exempt or zero-rated 계산서 driven by VAT posting setup rather than a manual user choice at issuance time

Supply amount and VAT amount carried as separate values end to end, matching the NTS schema instead of a single gross figure

Event subscribers on sales posting create the e-tax invoice record automatically, with an opt-out per customer or document type for out-of-scope supplies

Connector codeunit calling your certified ASP or Hometax-facing gateway over HTTPS with credentials in Isolated Storage — tax data never routes through ECOSIRE systems

Job queue entry polls transmission status and writes approval number (승인번호), NTS timestamp, and result code back onto the posted invoice

Issuance state (Queued, Issued, Accepted, Rejected) shown on the posted sales invoice card and factbox, so finance works from the document they already use

Korean-language tax invoice report layout rendered from the same record as the transmitted payload, so the customer PDF and the filed document cannot diverge

Corrective invoice (수정세금계산서) workflow with statutory correction reason codes — cancellation, amount change, buyer detail correction — each linked to the original approval number

NTS result codes translated into actionable messages on a dedicated e-Tax Invoice list page, with retry and re-issue actions guarded by permission set and protected against double issuance

Immutable archive table storing the exact request and response payload bytes, timestamp, and triggering user for the statutory retention period

API page (REST API v2.0 / OData v4) exposing issuance and archive records to Power BI, Dataverse, or an auditor extract without a database dump

Separate permission sets for issuance, channel configuration, and read-only audit access

Telemetry signals to your Application Insights for transmission failure, rejection, and stalled queue entries, so problems surface before the filing deadline

Buffered batch issuance for high-volume days with per-invoice failure isolation — one bad record does not block the run

Built to order, done for you

No DIY setup — a working app, built, installed and supported by ECOSIRE.

You order

Start with a one-time build price. We scope it with you at kickoff.

We build & install

ECOSIRE builds, configures and installs it on your Dynamics 365 Business Central.

Go live + support

You go live in about 2–4 weeks, with a post-launch support window.

About this Product

Korean VAT law requires corporate taxpayers and most individual businesses to issue electronic tax invoices and transmit them by the day after issuance, with penalties assessed per invoice for late or missing transmission. Dynamics 365 Business Central posts a sales invoice, produces a document number, and stops there. There is no Korean business registration number (사업자등록번호) structure on the customer card, no distinction between a 세금계산서 and a 계산서 for exempt or zero-rated supply, no NTS-shaped payload, no transmission state on the posted document, and no place to record the approval number (승인번호) the National Tax Service returns. Finance teams close the gap with an operator keying invoices into Hometax by hand, or an ASP screen that lives outside the ERP — either way the ledger and the tax filing drift apart, and the quarterly VAT return becomes a spreadsheet reconciliation exercise.

ECOSIRE builds an AL extension that makes the e-tax invoice a first-class part of the posting flow. Table and page extensions add the Korean fields Business Central lacks: business registration number with checksum validation, sub-business (종사업장) code, taxation type per line, and supply amount and VAT amount held separately as the NTS schema expects. A Korea E-Tax Setup page holds environment (test or production), channel credentials, certificate references, the issuance numbering series, and the mapping rules. Event subscribers on sales posting create a queued e-tax invoice record; a builder codeunit assembles the payload from posted lines and applies the tax mapping; a connector codeunit transmits it to your certified ASP or Hometax-facing gateway over HTTPS using credentials held in Isolated Storage in your own tenant — your tax data does not route through ECOSIRE infrastructure. A job queue entry polls for status and writes the approval number, NTS timestamp, and result code back onto the posted invoice, so a finance user sees Issued, Accepted, or Rejected on the document they already work from.

One posting produces both outputs. The machine format is the structured payload the tax authority receives; the human-readable format is a Business Central report layout of the Korean tax invoice rendered from the same record, so the PDF the customer receives can never disagree with what was filed. Rejections are treated as work, not as an error log: a rejected invoice lands in a Korea E-Tax Invoice list with the NTS result code translated into plain language, and a correction action creates the appropriate corrective document (수정세금계산서) carrying the statutory correction reason and a link back to the original approval number, so the chain stays traceable at audit. Cancellation, amount change, and buyer-detail correction each map to their own reason code rather than collapsing into a generic credit memo.

Archiving is built for the long statutory retention period Korean practice expects. Every transmission, response, and correction is written to an immutable log table with the exact payload bytes, timestamp, and the user who triggered it; the log is exposed through a dedicated API page (REST API v2.0 / OData v4) so an auditor extract, a Power BI report, or a Dataverse-connected review app can read it without a database export. Permission sets separate the accountant who issues from the administrator who configures the channel, and telemetry is emitted to your Application Insights so a failed transmission surfaces as an alert rather than as a surprise at filing time.

This is a build-to-order engagement, not an AppSource download. We start with a scoping call to confirm your Business Central version and deployment (SaaS or on-premises), your ASP or gateway of choice, which supply types you actually issue, and how your customer master carries registration numbers today. From confirmed scope, typical delivery is two to four weeks: we build against your release wave, install into a sandbox, run UAT with your finance team over real document flows including a deliberate rejection and correction cycle, then deploy to production with a rollback plan. You receive the AL source, the git repository, and a post-go-live support window.

What you get

Installable AL extension source built and compiled against your specific Business Central version and deployment type (SaaS per-tenant extension or on-premises)

Installation and configuration on your sandbox and production environments, including the ASP/gateway channel, numbering series, and VAT-to-taxation-type mapping

Technical documentation: object ID range, table and page extension inventory, event subscribers used, payload field mapping, and the connector interface for future maintenance

Korean e-Tax user guide for finance staff plus one live training session covering issuance, rejection handling, and the correction workflow

UAT executed on staging with your team, including a deliberate rejection and corrective-invoice cycle, and a documented rollback plan

Post-go-live support window for defect fixes and configuration adjustments, agreed at scoping

Git repository handover with full commit history, branch structure, and build pipeline configuration

Permission set definitions with a recommended role assignment matrix for issuer, administrator, and auditor

Who this is for

Finance Manager, Korean subsidiary of a multinational

Runs the local books in Business Central while group reporting happens elsewhere. Needs Korean e-tax invoices issued and transmitted on time without maintaining a parallel Hometax process, and needs approval numbers visible in the ERP so the local VAT return reconciles to the ledger without a spreadsheet.

Group Controller or Tax Compliance Lead

Accountable for penalty exposure across entities. Wants transmission failures to raise an alert the same day, an immutable archive that survives an NTS audit, and evidence that the PDF sent to the customer matches exactly what was filed.

IT Manager or Business Central partner consultant

Owns the tenant and the upgrade path. Needs a properly structured AL extension with a known object range, event subscribers rather than base-app modification, a documented API surface, and source in a repository they can maintain or hand to another developer.

AR or Billing Supervisor

Issues dozens to hundreds of invoices a day and is the first person to see a rejection. Needs the NTS result code in language they can act on, and a correction workflow that produces the right statutory document without asking accounting which reason code applies.

How South Korea e-Tax Invoice (Hometax) Compares

Criterion	ECOSIRE	Custom Build	Competitor	Dynamics 365 Business Central Native
Korean e-tax fields (registration number, sub-business code, taxation type)	Extension objects with checksum validation, mapped from your existing master data at scoping	Achievable, but the field structure and NTS schema mapping is research your developer does from scratch	Usually present, in a fixed shape your master data must adapt to	Not present — no Korean registration number or taxation type structure exists
Transmission channel	Built against your ASP or gateway, credentials in your tenant, data never routed through us	Yours to design and secure, including credential storage and retry semantics	Often the vendor's own gateway, bundling the software and the transmission relationship	No transmission capability at all
Rejection and correction workflow	NTS codes translated to plain language, statutory reason codes, corrective invoice linked to the original approval number	Built to the depth your budget allows; correction reason logic is usually the part that gets deferred	Typically covered, though reason-code handling varies and may not match your document flow	None — a rejection has nowhere to land
Archive and audit trail	Immutable log of exact payload bytes, response, timestamp and user, exposed via an API page for auditors	Depends entirely on what was specified; retention is often an afterthought	Usually retained in the vendor's portal rather than inside your Business Central database	Standard change log only — no payload retention
Upgrade survivability	Event subscribers and extension objects; release-wave validation included in the support window	Sound if built well, fragile if base-app objects were touched to hit a deadline	Vendor-managed, on the vendor's timetable rather than yours	Not applicable
Source code ownership	Full AL source plus git repository handover — maintain it yourself or move it	Yours by definition, along with all of the maintenance	Closed; you hold a licence, not the code	Not applicable
Time to a running system	Typically 2-4 weeks from confirmed scope, including UAT on your staging environment	Commonly two to four months once schema research, testing, and iteration are counted	Fast to install, then a fitting period while your process bends to the app	Immediate, but the compliance work stays manual in Hometax
Fit to your document flow	Scoped to your supply types, entities, and posting practice before a line of code is written	Exact fit, at the cost of building every part yourself	Generic fit; sub-business codes or mixed taxable and exempt lines may need a workaround	No fit — the flow ends at posting

Frequently Asked Questions about South Korea e-Tax Invoice (Hometax)

How long does delivery take?

This is build-to-order, not an instant download. Typical delivery is two to four weeks from confirmed scope. The clock starts once we have agreed your Business Central version and deployment type, your ASP or gateway, which supply types are in scope, and how your customer master carries registration numbers. Larger scopes — multiple legal entities, sub-business codes, or a non-standard gateway — are quoted with their own timeline at the scoping call.

Does ECOSIRE transmit our tax data to the NTS on our behalf?

No. The extension calls your certified ASP or Hometax-facing gateway directly from your Business Central tenant, using credentials you hold, stored in Isolated Storage. Your tax data does not route through ECOSIRE infrastructure. We build, configure, and support the connector; the tax relationship and the transmission channel remain yours.

Does this work on Business Central SaaS, on-premises, or both?

Both. On SaaS it is delivered as a per-tenant extension, or as an AppSource-shaped app if you prefer that path, built against your current release wave. On-premises we build against your specific version and provide the compiled .app plus deployment instructions. Outbound HTTPS to your ASP endpoint is required either way; on-premises that usually means a firewall rule.

What happens when Microsoft ships a new release wave?

The extension uses event subscribers and extension objects rather than base-app modification, which is what keeps upgrades survivable. During your support window we validate it against the next release wave and fix any breaking change at no charge. After the window, compatibility updates are available as a maintenance agreement or a fixed-scope update engagement — your choice, and you hold the source either way.

How are rejected invoices and corrections handled?

A rejection is written back onto the posted invoice with the NTS result code translated into plain language, and the record appears in the e-Tax Invoice list for action. The correction action then creates the appropriate 수정세금계산서 with the statutory reason code — cancellation, amount change, or buyer detail correction — carrying a link to the original approval number so the chain stays traceable at audit. Retries are guarded so a transient failure cannot double-issue.

We already have an ASP contract. Can you integrate with it rather than choose one for us?

Yes, and that is the usual case. The connector sits behind a clear interface precisely so the gateway is a configuration decision rather than a rebuild. Bring your ASP's API documentation and test credentials to the scoping call and we build against it. If you have not selected one yet, we scope against whichever you choose.

Do we get the source code?

Yes. You receive the full AL source and the git repository with commit history at handover, along with technical documentation covering the object range, event subscribers, and payload mapping. You are not locked to ECOSIRE for future maintenance — another partner or your own developer can pick it up.