AEAT and Paris School of Economics: what they are investigating and how it could affect your tax situation

Key data

The Tax Agency and the International Tax Observatory of the Paris School of Economics have formalized a joint research agreement on the progressivity of the Spanish tax system. The resolution publishing it was published in the Official State Gazette on June 23, 2026, effective that same day.

This agreement is not a tax change in itself: it does not modify tax rates, does not create new obligations, and does not alter declaration deadlines. However, its strategic relevance is high: the data that the AEAT makes available to the Paris researchers will serve as the basis for analyzing how progressive—or regressive—the Spanish tax system is, and those conclusions could translate into tax reform proposals with real impact on companies and taxpayers.

What does this regulation establish?

The agreement formalizes collaboration between two institutions to develop joint research on tax policy in Spain, with specific focus on the progressivity of the tax system. The key elements of the agreement are:

• Transfer of tax data by the AEAT: The Tax Agency will provide tax data to the research team. This data will always be aggregated and anonymized, meaning it will in no case allow identification—neither directly nor indirectly—of specific natural or legal persons.
• Legal basis for transfer: The transfer of information is carried out under the Public Statistical Function Act, which regulates the use of data for statistical and research purposes.
• Previous institutional framework: The agreement is framed within a Memorandum of Understanding signed in February 2026 between the Paris School of Economics (PSE) and the State Secretariat for Finance, which already established the basis for collaboration.
• Data protection guarantees: Strict mechanisms are established to prevent any direct or indirect identification of taxpayers, both natural and legal persons.
• Final objective: The results of the research could influence future tax reforms and Spanish tax policy.

The International Tax Observatory of the Paris School of Economics is one of the world's leading centers for analyzing tax inequality and the distribution of the tax burden. Its methodology—internationally known for work on wealth concentration and tax evasion—applied to real AEAT data can generate high-impact empirical evidence.

Economic and operational impact

In the short term, this agreement generates no direct cost or obligation for companies or taxpayers. There are no new taxes, no changes in rates or taxable bases.

The real impact is strategic and will materialize in the medium and long term:

• Evidence-based tax reforms: If the study concludes that the Spanish system is less progressive than desirable—for example, that capital income is taxed proportionally less than labor income—this could translate into concrete legislative proposals: increases in personal income tax rates for high incomes, changes in corporate income tax, review of tax benefits, or modifications in the treatment of dividends and capital gains.
• Greater scrutiny of major taxpayers: Research on progressivity typically focuses on the upper income and wealth brackets, as well as complex business structures. The conclusions can strengthen political pressure to reduce the gap between nominal and effective rates.
• Signal of political direction: The fact that the Finance Ministry signed this agreement in February 2026 and formalized it in June indicates an institutional willingness to have solid technical arguments for future reforms. It is not a neutral move.

Who does it affect?

• Large companies and business groups: Especially those with optimized tax structures, since progressivity studies typically analyze the gap between nominal and effective rates in corporate income tax.
• High-income taxpayers: Analysis of progressivity in personal income tax typically focuses on upper brackets and the treatment of capital income versus labor income.
• Tax advisors and tax consulting firms: They must anticipate the scenario of reforms that may result from the study and prepare their clients.
• CFOs and financial directors: Medium-term tax planning may be affected if the study's conclusions lead to regulatory changes.
• Tax researchers and academics: The agreement opens a new source of empirical data on the Spanish tax system.
• Tax administration: The AEAT strengthens its analytical capacity and its position as a source of data for tax policy design.

Practical example

Imagine a mid-sized technology company with a taxable base in corporate income tax of 2 million euros. Its nominal rate is 25%, but thanks to deductions for R&D, accelerated depreciation and other tax incentives, its actual effective rate is around 14%.

A progressivity study prepared with real AEAT data—such as the one that the International Tax Observatory will develop—can quantify exactly how many companies are in this situation and what revenue impact reducing that gap would have. If the conclusions point to the average effective rate of large companies being significantly lower than the nominal rate, the legislator will have solid technical arguments to limit deductions or establish minimum effective rates, following the wake of the European directive on global minimum taxation (Pillar II).

For that technology company, the risk is not today: it is when the study's conclusions translate into a legislative proposal. Anticipating that scenario—reviewing the tax structure and evaluating which deductions are most vulnerable—is the smart action.

What should companies do now?

1. Do not act immediately, but do monitor: This agreement generates no obligations today. However, it marks a clear direction for tax policy. Set up an alert to follow publications by the International Tax Observatory of the Paris School of Economics on Spain.
2. Review the gap between nominal and effective rate in corporate tax: If your company has an effective rate significantly lower than the nominal rate thanks to deductions or tax structures, evaluate with your advisor what part of that advantage could be in the sights of future reforms.
3. Anticipate tax reform scenarios: Have your tax advisor conduct a sensitivity analysis: how would a reduction in corporate deductions affect your bottom line? Or an increase in the minimum effective rate? Having that analysis done before the reform arrives is a competitive advantage.
4. Verify compliance with data protection guarantees: Although the transfer of AEAT data to the Observatory is guaranteed to be anonymous, if your company manages tax data of third parties, ensure that your internal data protection protocols are up to date.
5. Follow the evolution of the Memorandum of Understanding: The agreement published in June 2026 is framed within the Memorandum signed in February 2026 between the PSE and the State Secretariat for Finance. Any further development of that framework could anticipate new legislative initiatives.

Official source

View complete regulation at official source

Disclaimer: This article is for informational purposes only and does not constitute legal advice. For specific decisions, consult a qualified professional. Source: https://www.boe.es/diario_boe/txt.php?id=BOE-A-2026-13621