Changes to MDR. How should tax arrangements be reported after 1 October 2026?

On 1 October 2026, amendments to the Polish Tax Ordinance Act and corresponding changes to the Fiscal Penal Code concerning tax arrangements, commonly referred to as Mandatory Disclosure Rules (MDR), will enter into force in Poland. Since they were first introduced, MDR provisions have raised numerous practical and interpretative concerns. In response, the legislative has decided to endorse certain simplifications for businesses and align the Polish MDR framework more closely with the provisions of the DAC6 Directive.

Has the government actually succeeded in simplifying the tax arrangement reporting regime? In this article, we seek to answer this key question while also focusing, from the perspective of experienced tax advisors, on an issue that is often overlooked: the transitional provisions and the potential tax risks that may arise in connection with the upcoming changes.

What will change in MDR reporting as of 1 October 2026?

The amendments to the Tax Ordinance introduced in October are broad in scope and far-reaching. Certain MDR obligations have been repealed or limited, some definitions revised, while others – consolidated.

The most significant changes to the tax arrangement reporting regime:

• Abolition of the obligation to report domestic tax arrangements – only cross-border arrangements will be subject to reporting obligations.
• Removal of the "other specific hallmarks" category.
• Repeal of penalties for failure to have a mandatory internal MDR procedure in place, following the abolition of the requirement to implement and apply such a procedure.
• Abolition of the obligation to submit MDR-2 notifications.
• Exclusion of the possibility of obtaining individual tax rulings on MDR matters.
• Exclusion of VAT and excise duty from the scope of the MDR provisions.
• Introduction of the possibility for MDR-3 information to be signed by an authorised representative.
• Change to the deadline for submitting MDR-3 information.
• Merger of the roles of promoter and supporting entity – following the amendments, only the role of promoter will remain, in line with the framework of the DAC6 Directive, although the promoter's responsibilities will be significantly expanded to include obligations previously imposed on supporting entities.
• Changes to key definitions – including the definitions of the main benefit test, tax benefit and arrangement.
• Changes regarding professional secrecy – in certain circumstances, a promoter who is an attorney-at-law, legal counsel, tax advisor or patent attorney will not be obliged to report a tax arrangement.

Although the above changes represent only part of the reform, in our view they are among the most significant and require particular attention from taxpayers conducting business in Poland.

Between the old and new MDR rules. How to navigate the transitional period?

Determining the appropriate course of action during the transitional period is particularly important. The new regulations not only lift some MDR obligations, primarily by abolishing the requirement to report domestic tax arrangements and the requirement to maintain an internal MDR procedure, but also change the deadline for submitting MDR-3 information.

Does this mean that, after 1 October 2026, businesses will no longer be exposed to penalties for failing to report a domestic tax arrangement?

No. The existing provisions will remain in force until the end of September 2026. This means that if the deadline for reporting a tax arrangement falls on 30 October 2026, the existing rules will continue to apply and the arrangement must therefore be reported.

Importantly, however, if such a domestic tax arrangement is reported before the new regulations enter into force, the beneficiary will no longer be required to submit MDR-3 information in respect of that arrangement. This exemption applies only to MDR-3 information for 2026.

New deadline for filing MDR-3 information

Potential penalties for failing to report a tax arrangement are not the only issue taxpayers should be aware of. Beneficiaries may also have concerns regarding the deadline for filing MDR-3 information in respect of cross-border arrangements.

Under the current rules, MDR-3 information is generally submitted together with the tax return for a given tax year, relating to the tax to which the reportable arrangement pertains. Under the new regulations, however, the MDR-3 form must be submitted by the end of the fourth month following the end of the taxpayer's tax year, regardless of the type of tax concerned. The transitional provisions are also helpful in this respect, as they explicitly state that, from the date the October amendments enter into force, MDR-3 disclosures will be subject to the new rules. Consequently, as of 1 October 2026, MDR-3 information must be filed no later than by the end of the fourth month following the end of the taxpayer's tax year.

What about the internal MDR procedure?

Another issue giving rise to considerable uncertainty concerns the mandatory internal MDR procedure.

The new regulations do not contain any transitional provisions regarding the obligation to maintain an internal MDR procedure. As a result, there is currently no clear guidance on whether entities that were required to implement such a procedure between January 2019 and September 2026, but failed to do so, will still be obliged to fulfil this requirement.

New obligations for promoters

Another important issue is the transition of an entity performing the role of a service provider in a tax arrangement until 30 September 2026 into an entity performing the role of the promoter of the tax arrangement from 1 October 2026. This change will entail a significant shift in the scope of its obligations.

Changes to penalties for non-compliance with MDR obligations

A significant amendment has also been introduced to the Fiscal Penal Code, expanding the circumstances in which financial penalties may be imposed. From 1 October 2026, fines may be imposed not only for failure to submit MDR-3 information, but also for submitting such information after the statutory deadline. Unfortunately, the amended regulations do not provide for transitional rules addressing MDR-3 disclosures that should have been submitted under the currently applicable provisions but remain outstanding.

How to prepare for the MDR changes?

The upcoming MDR amendments provide a good opportunity for organisations to reassess their historical approach to MDR compliance and verify whether they have conducted appropriate analyses to identify reportable tax arrangements and fulfil related reporting obligations. The existing fiscal penal sanctions for non-compliance with MDR obligations remain applicable and may be severe.

The next step, during the transitional period, should be to take measures aimed at protecting the organisation against tax risks arising from the amendments and the absence of certain important transitional provisions.

It is also advisable to prepare or update internal guidelines and procedures to ensure the correct application of the revised MDR regulations once they enter into force.

Furthermore, it cannot be ruled out that tax authorities will pay closer attention to MDR compliance following the reform, particularly in light of the abolition of the obligation to report domestic tax arrangements. Authorities may intensify their verification activities to determine whether taxpayers have properly fulfilled all MDR-related obligations. As domestic arrangements will no longer fall within the reporting regime, the overall number of reportable arrangements is expected to decrease significantly. Consequently, tax authorities may be able to focus their resources more effectively on analysing and reviewing a smaller number of filings.

RSM Poland tax advisors strongly believe that the coming months should therefore be viewed as an excellent opportunity to streamline tax arrangement reporting processes and to implement relevant procedures or MDR regulations within the organisation.