South Korea's Qualified Domestic Minimum Top‑up Tax (QDMTT) 2026: Compliance Checklist for Multinational Groups

South Korea’s implementation of the global minimum tax marks one of the most consequential shifts in the country’s international tax landscape in decades. By enacting a Qualified Domestic Minimum Top‑up Tax (QDMTT) as part of its broader Pillar Two adoption, Korea has given itself the right to collect a top‑up tax on multinational enterprise (MNE) groups whose effective tax rate on Korean-sourced income falls below the 15 percent global floor. The first QDMTT reporting and filing obligations fall due in 2026, meaning that CFOs, general counsel and group tax directors who have not already mobilised compliance workstreams face immediate exposure.

This guide provides the practical, lawyer‑led governance and compliance playbook that in‑house teams need, covering who is in scope, what must be filed, how the QDMTT interacts with Korea’s existing corporate tax rules, and the board‑level actions required to meet every deadline.

Key Takeaways, What to Do in the Next 30, 90 and 365 Days

Before diving into the technical detail, the following executive summary identifies the three most urgent action horizons for any MNE group with Korean constituent entities.

• Within 30 days, Scope and ownership. Confirm whether the group meets the consolidated revenue threshold (€750 million in at least two of the four preceding fiscal years). Identify every Korean constituent entity. Appoint a Pillar Two project lead (typically group tax director or general counsel) and convene a kick‑off meeting with treasury, tax, legal and external advisors.
• Within 90 days, Data and governance. Begin jurisdictional effective tax rate (ETR) modelling for each Korean entity. Collect financial and tax data for the first applicable fiscal year. Draft and circulate a board resolution authorising the group’s QDMTT compliance framework, delegation of filing authority, and budget allocation for external advisory support.
• Within 365 days, Filing and audit readiness. Complete and submit the GloBE Information Return (GIR) and the local QDMTT return through Korea’s National Tax Service (NTS) e‑filing system. Reconcile the QDMTT calculation with the corporate tax return. Archive supporting documentation, transfer pricing files, ETR workpapers, and board minutes, in anticipation of NTS audit scrutiny.

The QDMTT is Korea’s domestic mechanism that allows the Korean tax authority, rather than the ultimate parent entity’s home jurisdiction, to collect the top‑up tax. Where a properly designed QDMTT is in place, it takes priority in the Pillar Two sequencing, reducing or eliminating the top‑up otherwise collectible under the Income Inclusion Rule (IIR) or the Undertaxed Profits Rule (UTPR) by other jurisdictions. Industry observers expect that Korea’s early adoption will serve as both a revenue‑protection measure and a signal to treaty partners that Korean‑sourced income is subject to an internationally compliant minimum tax.

What Is the QDMTT and Who Is in Scope Under the Global Minimum Tax in South Korea?

The Qualified Domestic Minimum Top‑up Tax is the centrepiece of South Korea’s Pillar Two implementation. It operates by measuring the jurisdictional ETR of each MNE group’s Korean constituent entities against the 15 percent minimum rate. Where the Korean ETR falls below that floor, typically because of tax incentives, credits, or timing differences, the QDMTT imposes a top‑up equal to the difference, applied to the group’s excess profit in Korea.

Legal Basis and Effective Dates

Korea’s Pillar Two framework was enacted through amendments to the Adjustment of International Taxes Act (국제조세조정에 관한 법률) and its subordinate presidential decree. These amendments transpose the OECD/G20 Inclusive Framework’s GloBE Model Rules into Korean domestic law. The legislation applies to fiscal years beginning on or after 1 January 2024, which means the first full fiscal year subject to the rules has already closed for December year‑end groups. The first filing and reporting obligations, the GIR and the local QDMTT return, fall due in 2026, aligning with the corporate tax reporting calendar administered by the NTS.

The Ministry of Economy and Finance (MOF) has published accompanying guidance and implementation decrees, while the NTS has issued operational notices on filing mechanics and data requirements. Groups should monitor the NTS website for updated templates and electronic filing specifications as they become available.

In‑Scope MNE Threshold and Constituent Entity Tests

Not every multinational group operating in Korea is subject to the QDMTT. The rules adopt the same scope tests as the OECD GloBE Model Rules, centred on consolidated group revenue.

Groups that do not meet the €750 million revenue threshold remain outside scope. However, the likely practical effect will be that fast‑growing groups, particularly in Korea’s technology, semiconductor and renewable energy sectors, should reassess their status annually, as crossing the threshold in any two of four years triggers immediate inclusion.

Key Dates and Filing Timeline for South Korea Tax 2026 Obligations

Timing is the single most critical compliance variable for the global minimum tax in South Korea. The following timeline sets out the key milestones from the legislation’s enactment through the first reporting cycle and beyond.

The filing and payment deadlines for the QDMTT return follow Korea’s corporate tax reporting calendar. For entities with a December fiscal year‑end, the corporate tax return is generally due within three months after the close of the fiscal year, with extensions available in certain circumstances. The GIR filing timeline aligns with the group’s reporting obligations, typically due within 15 months of the close of the fiscal year (with an extended 18‑month window for the first transitional year), consistent with the OECD GloBE framework.

Groups should note that the transitional safe‑harbour provisions, which may exempt certain jurisdictions from full GloBE calculations in the initial years, require a positive election and supporting data. Failing to make a timely election forfeits the safe‑harbour benefit for the relevant fiscal year.

How the QDMTT Interacts with IIR, UTPR, Transfer Pricing and Tax Treaties

Understanding how Korea’s QDMTT sits within the broader Pillar Two architecture is essential for multinational compliance. The QDMTT does not operate in isolation, it interacts with the IIR, the UTPR, domestic tax credits, transfer pricing rules and Korea’s extensive network of double taxation agreements (DTAs).

Interaction with Corporate Tax Credits and Domestic Tax Base Adjustments

South Korea offers a range of tax incentives, notably R&D credits, investment tax credits for facility expansion, and regional development incentives. These credits reduce the domestic covered taxes paid by constituent entities, which in turn lowers the jurisdictional ETR. Where the ETR after credits falls below 15 percent, the QDMTT tops up the difference.

Early indications suggest that this creates a tension for policymakers: generous incentive regimes that historically attracted foreign investment may now be partially offset by the QDMTT itself. For in‑house teams, the practical consequence is that every tax credit claim must be modelled not just for its corporate tax benefit but also for its ETR impact. A credit that saves ₩100 million in corporate tax but triggers ₩80 million in QDMTT delivers a net benefit of only ₩20 million, a dramatically different return on the compliance effort required to claim it.

Transfer Pricing Implications

Transfer pricing adjustments directly affect the computation of jurisdictional GloBE income, and therefore the ETR. If a Korean constituent entity’s taxable income is increased by a TP adjustment (whether initiated by the NTS or by a foreign tax authority on the counterparty), the numerator (covered taxes) remains unchanged while the denominator (GloBE income) rises, depressing the ETR and potentially increasing the QDMTT liability.

Conversely, a corresponding adjustment that increases Korean taxable income and triggers additional Korean corporate tax may raise both the numerator and denominator, with a net effect that depends on the relative magnitudes. Groups must maintain contemporaneous TP documentation and run sensitivity analyses modelling the QDMTT impact of plausible TP outcomes.

The following worked example illustrates the mechanics:

This example demonstrates how a relatively modest TP adjustment can swing a group from zero QDMTT liability to a material top‑up. Corporate tax reporting in Korea now requires integrated TP and QDMTT modelling.

Tax Treaties and Treaty Relief

Korea has one of the most extensive DTA networks in Asia, with treaties in force with over 90 jurisdictions. A common question is whether treaty relief, such as reduced withholding rates on dividends, interest and royalties, affects the QDMTT calculation. The answer is nuanced.

Treaty relief that reduces Korean withholding tax on outbound payments does not directly reduce the covered taxes of the Korean constituent entity (those taxes are borne by the foreign recipient). However, treaty relief that affects the domestic tax base, for example, through permanent establishment attribution rules or the allocation of business profits, can change both GloBE income and covered taxes, with knock‑on ETR effects.

The QDMTT itself is generally not subject to treaty override. The OECD’s position, adopted in the GloBE Model Rules commentary, is that the QDMTT, as a domestic top‑up mechanism designed to secure the minimum rate, falls outside the scope of traditional DTA limitations. Korea’s implementation follows this approach.

Safe‑Harbour and Sequencing Rules: Does Korea’s QDMTT Reduce IIR or UTPR Exposure?

Under the Pillar Two sequencing framework, a jurisdiction’s QDMTT is credited first. If Korea collects the full top‑up domestically through its QDMTT, the parent jurisdiction’s IIR obligation is reduced to zero for Korea, and the UTPR backstop does not apply. This makes Korea’s QDMTT a strategically significant compliance advantage: a well‑functioning QDMTT means the group does not face double collection risk across jurisdictions.

Transitional safe‑harbour rules also apply. For the initial period, groups may elect to use simplified calculations based on Country‑by‑Country Reporting (CbCR) data, qualified financial statements, or a routine profits test. If any safe‑harbour test is met, the jurisdictional top‑up for Korea is deemed to be zero for that fiscal year, significantly reducing the compliance burden.

Corporate Governance and Board‑Level Requirements for Global Minimum Tax Compliance

Global minimum tax compliance is not solely a tax department function. It requires board oversight, cross‑functional coordination, and formal corporate governance actions, particularly for Korean subsidiaries of foreign‑parented groups, where the local board must ensure the entity meets its domestic filing obligations.

Board Responsibilities and Timing

The board of each Korean constituent entity should formally acknowledge the group’s Pillar Two obligations and delegate authority for QDMTT compliance to a named officer or committee. This is not merely best practice, it creates an auditable governance trail that the NTS may request during an examination.

Industry observers expect that boards should address QDMTT compliance at the first board meeting following the close of each fiscal year, with a standing agenda item covering ETR estimates, anticipated top‑up amounts, and any safe‑harbour elections.

Legal and Internal Controls

Effective multinational compliance requires clear allocation of responsibilities across functions:

• Tax department. Owns the ETR calculation, GIR data preparation, and QDMTT return filing.
• Treasury. Manages cash flow for top‑up tax payments and monitors intercompany financing structures that affect ETR.
• Legal / General Counsel. Oversees governance compliance, reviews board resolutions, ensures TP documentation is current, and manages audit responses.
• External advisors. Provide technical review of ETR calculations, assist with safe‑harbour elections, and support dispute resolution.
• Finance / ERP team. Configures data extraction routines for GloBE income, covered taxes, and SBIE components.

Suggested Board Resolution Template

The following template provides a starting point for the board resolution. It should be adapted to the specific corporate structure and governance requirements of the entity:

“RESOLVED, that the Board acknowledges the Company’s obligations under the Adjustment of International Taxes Act, as amended, implementing the OECD Pillar Two GloBE rules, including the Qualified Domestic Minimum Top‑up Tax. The Board hereby authorises [Named Officer/Committee] to (i) collect and prepare all data required for the GloBE Information Return and the local QDMTT return; (ii) file such returns and make corresponding payments to the National Tax Service within the prescribed deadlines; (iii) make safe‑harbour elections where eligible and in the Company’s interest; and (iv) engage external advisors as necessary. [Named Officer/Committee] shall report to the Board on QDMTT compliance status at each regular board meeting.”

Immediate Governance Actions, Top 10 Checklist

• 1. Confirm group revenue threshold status and in‑scope determination.
• 2. Identify all Korean constituent entities (subsidiaries, branches, PEs).
• 3. Appoint a Pillar Two project lead with cross‑functional authority.
• 4. Pass a board resolution authorising QDMTT compliance (see template above).
• 5. Map data sources for GloBE income and covered taxes in the ERP system.
• 6. Run a preliminary jurisdictional ETR estimate for the first applicable fiscal year.
• 7. Assess eligibility for transitional safe‑harbour elections.
• 8. Review all active tax credits, incentives and withholding tax positions for ETR impact.
• 9. Update TP documentation to include QDMTT sensitivity analysis.
• 10. Calendar GIR and QDMTT return deadlines and assign filing responsibility.

Practical Compliance Playbook and Entity‑Level Filings

Once governance structures are in place, the compliance workstream shifts to execution. This section provides the operational detail that tax and legal teams need to file accurately and on time.

Domestic Constituent Entity Obligations

Each Korean constituent entity that is part of an in‑scope MNE group must prepare and file a local QDMTT return with the NTS. The return captures the entity’s GloBE income, covered taxes, SBIE deductions, and the resulting top‑up tax (if any). The NTS has indicated that the QDMTT return will be filed as a supplementary schedule to the annual corporate tax return, using designated forms and the NTS e‑filing system (홈택스 / Hometax).

Penalties for non‑compliance follow the existing framework under Korea’s tax administration rules. Late filing attracts administrative penalties, and understatement of QDMTT liability may result in additional tax, interest, and potential penalties for negligent or intentional under‑reporting. The NTS has flagged Pillar Two filings as a priority audit area, and industry observers expect heightened scrutiny during the initial filing years.

Data and Systems Requirements

The GIR requires a substantial volume of data that many groups do not currently extract in the required format. Key data fields include:

• GloBE income / loss. Adjusted from financial accounting income per the entity’s qualified financial statements, with prescribed add‑backs and deductions.
• Covered taxes. Current tax expense, deferred tax adjustments, and allocated taxes attributable to the Korean jurisdiction.
• SBIE components. Eligible payroll costs and carrying value of tangible assets located in Korea.
• Entity‑level details. Ownership structure, entity classification, and intercompany transaction data.

Groups should configure ERP data extraction routines well in advance of the filing deadline. Where legacy systems cannot produce the required outputs, manual workarounds and spreadsheet reconciliations should be documented for audit purposes.

Audit and Dispute Readiness

Maintaining a traceable audit trail is critical. The following documents should be archived for each fiscal year:

• ETR workpapers. Full calculation showing GloBE income, covered taxes, ETR, top‑up percentage, and QDMTT liability.
• TP documentation. Including QDMTT sensitivity analysis and documentation of arm’s length pricing for material intercompany transactions.
• Board minutes. Evidence of governance oversight, including board resolutions, committee reports, and safe‑harbour election decisions.
• Reconciliation schedules. Bridging the entity’s financial statements to the corporate tax return and to the QDMTT return.

Cross‑Border Transactions and Restructuring Under the Global Minimum Tax in South Korea

Pillar Two and the QDMTT have material implications for how multinational groups structure cross‑border transactions involving Korean entities. Deals, treasury arrangements and IP structures that were tax‑efficient under the pre‑QDMTT regime may now produce unintended top‑up liabilities.

M&A Considerations

Acquirers of Korean businesses should include QDMTT modelling in their due diligence. Key areas include: historical ETR analysis (to identify latent top‑up exposure), review of existing tax incentives and credits that may depress the ETR post‑acquisition, and assessment of whether the target’s constituent entity status changes upon deal completion. Sale and purchase agreements should include QDMTT‑specific representations, warranties and indemnities, particularly covering pre‑completion fiscal years where the QDMTT return has not yet been filed.

Treasury and Intercompany Finance

Intercompany financing structures are a common source of ETR pressure. Interest payments from a Korean entity to a related party in a low‑tax jurisdiction reduce Korean taxable income (and therefore GloBE income) without a proportionate reduction in covered taxes, potentially raising the Korean ETR. However, if thin capitalisation or interest limitation rules deny the deduction for Korean corporate tax purposes, GloBE income may be higher than expected, with complex knock‑on effects on the ETR calculation.

Groups should review all intercompany loan and guarantee arrangements to model their QDMTT impact and consider whether restructuring improves the overall group position. Jurisdictions that have adopted the OECD’s approach to global minimum tax compliance, such as those discussed in the context of the Spain Pillar Two deadline, provide useful comparative reference points.

Practical Structuring Red Flags

The following arrangements should be reviewed with particular urgency:

• IP migrations. Transferring intellectual property out of Korea to reduce domestic income may lower GloBE income but will also reduce covered taxes, with an uncertain net ETR effect and potential TP challenge risk.
• Profit‑shifting arrangements. Any structure that artificially reduces Korean taxable income will be scrutinised under both the existing TP rules and the new QDMTT framework.
• Treaty‑shopping structures. The QDMTT’s independence from treaty limitations means that treaty‑based structures designed to minimise Korean tax may no longer deliver the expected benefit once the QDMTT top‑up is factored in.

Any restructuring that affects constituent entity status, GloBE income allocation, or covered taxes requires board approval under the governance framework described above.

Conclusion and Next Steps

The global minimum tax in South Korea is no longer a policy discussion, it is a live compliance obligation. MNE groups with Korean constituent entities should treat the 2026 filing cycle as the highest‑priority tax governance workstream of the year, engaging qualified cross‑border tax and corporate counsel to ensure that every deadline is met and every governance step is documented.

Sources

1. National Tax Service (Korea)
2. Ministry of Economy and Finance (Korea)
3. OECD, Global Minimum Tax (Pillar Two)
4. OECD Korea Policy Centre
5. Australian Taxation Office, Pillar Two Guidance