International tax cooperation is a practice that has proven to have a significant impact on tax administrations’ compliance strategies. Today, it is undoubtedly one of the cornerstones of tax administrations, and the expectation is that tax administrations will increase their level of cooperation.

According to the Progress Report on the members of the Latin American Initiative of the Global Forum on Transparency and Exchange of Information for Tax Purposes (GF), revenues of EUR 578 million were reported in 2025 as a result of the use of information exchange upon request and the Common Reporting Standard (CRS).

Despite these advances, challenges remain. They must be addressed in order to continue leveling the playing field and facilitating cooperation among tax authorities. In international tax law, and particularly in international tax cooperation, the calculation of time limits is critical.
While the international standard on information exchange establishes a minimum retention period of five years for information and estimated timeframes for responding to requests for information, countries differ in how they calculate statutory limitation periods and expiration dates, as well as the timeframes for enforcement actions (e.g., investigations or audits). The differences are significant, even at the domestic level, where special regimes may exist (e.g., a recent reform in Argentina establishes a 3-year statute of limitations for taxpayers deemed compliant). In some countries, debts do not expire, while in others the statute of limitations may be shorter, the same, or significantly longer than the document retention period proposed by the GF. Additionally, the start of the fiscal year does not coincide with the calendar year in all countries (e.g., the U.S.). This situation can create obstacles when exchanging information or moving forward with mutual assistance procedures.

For example, when a considerable amount of time has elapsed between the time information is provided to another tax authority and the year to which that information relates, there is a risk that the statute of limitations for a period under audit will expire in the requesting country. In this case, if the requested information arrives after the legal deadline for taking enforcement actions and the requesting tax authority issues an assessment based on it, the taxpayer may challenge it by invoking the statute of limitations, without having to dispute the accuracy of the data. This situation can also put TAs officials at risk when, due to regulatory ambiguities regarding the calculation of time limits and/or reasonable tolerance margins for awaiting the requested information, a significant debt becomes time-barred or expires.

To avoid these difficulties and facilitate the exchange of information and mutual assistance, countries should review their respective rules governing the calculation of time limits (e.g., statutes of limitations, expiration, interruption, or suspension[1] and assess whether special rules are necessary in cases involving international cooperation. For example, in some countries, the submission of a request for information to address an audit case has an automatic suspensive effect on the statute of limitations (e.g., France). Likewise, it is important for them to assess the appropriateness of time limits for conducting complex audit actions. For example, several Latin American countries have different time limits for conducting audits of large companies, multinational companies, or international transactions.

Under ideal conditions, it would be advisable to promote an international effort to harmonize the calculation of time limits, which would help optimize the exchange of information upon request and, in particular, the planning of joint or simultaneous audits.

In practice, the administrative process involved in exchanging information upon request, depending on the case in question and/or country, may take longer than provided for in the international standard. This can occur, for example:

• • When the requested country needs to obtain a court order or follow a special procedure to access the information, or when a person affected by the exchange of information challenges the respect for their rights, in the context of a request .
• • When obtaining information about assets held abroad takes several months, especially if those assets are held through complex chains of ownership involving multiple jurisdictions.

In the examples cited, if the running of the deadlines is not suspended, the Tax Authority risks losing its powers of audit and collection before receiving evidence from abroad. Therefore, the provisions for the suspension or interruption of deadlines ensure that an audit procedure involving requests for information from abroad can be completed without time pressure. It also prevents a taxpayer from taking advantage of the delays caused by bureaucracy to evade their responsibilities. Suspension or interruption is also justified in the context of international cooperation procedures, when the delay is not attributable to the administration of the tax authority requesting the information.

It is important that, for example, the suspension period when filing a request for information consider the time it may take for the states involved to clarify a request for information that, according to the requested state, may constitute a “fishing expedition” or may not meet the principle of “foreseeable relevance.” This measure ensures that evidence obtained outside the standard timeframe remains valid for tax assessment purposes, since the statutory deadline was suspended.

Several countries have adopted different timeframes in their tax codes to address situations involving foreign assets. This approach balances the complexity of enforcement actions with the time required to access and process information from abroad. A similar approach is often considered in the context of using information obtained through automatic exchange of information (e.g., CRS, FATCA, CARF, etc.). In some countries, receiving information automatically may be considered grounds for interruption if the information received reveals undeclared assets that give rise to audit actions.

In light of the above, it would be advisable to:

• • The requesting State may suspend the time limit when submitting a request for information to another State, on the grounds that the latter State would be unable to complete its audit or settlement proceedings without access to the requested information. The suspension period expires when a response is received from the requested State or when the suspension period expires
• • Upon receiving a request for information, the requested administration must comply with the timeframes suggested by the standard for responding to it. When the information is not available at the TA, it is necessary to exercise verification and oversight powers to access it. In this case, the TA has no complete control over how long it may take to obtain this information. Therefore, if initiating an administrative proceeding to obtain the information is being considered, it would be appropriate to interrupt or suspend deadlines.
• • In the case of automatic exchange of information, automatic suspension should not apply because it does not involve a request for information. However, it is recommended that the suspension be applied if the tax authority detects risks and initiates an administrative audit.

The link between these concepts (suspension and statute of limitations) and the standard of transparency and information exchange aims to balance the need for tax transparency with due respect for taxpayers’ rights of defense. In this regard, the GF, on the one hand, promotes the need to interrupt or suspend deadlines and, on the other, in its peer reviews, monitors whether jurisdictions lack internal mechanisms that unnecessarily delay the provision of information.

In the context of international debt collection assistance, the Convention on Mutual Administrative Assistance in Tax Matters (MAC), in Article 14(2), provides that acts performed in the requested state to suspend or interrupt limitation periods shall have the same effect under the laws of the requesting state. This means that actions taken by the requested state have the effect of interrupting the limitation periods under the domestic laws of both states. The extension of the limitation period resulting from the interruption shall be determined in accordance with the provisions of the requesting state’s law.
Requests for assistance in collection do not affect the options available to the requesting state under its laws regarding the suspension or interruption of the aforementioned statute of limitations. Furthermore, when a taxpayer acknowledges obligations or requests payment arrangements, it should be possible for the requesting country to interrupt the statute of limitations. For its part, Article 27 of the Model Convention does not explicitly provide for the suspension or interruption of limitation periods.

Beyond the recommendation to extend deadlines through the mechanisms described above, it is necessary to establish limits to prevent an administrative audit from dragging on indefinitely. This safeguards the taxpayer’s legal certainty. For example:

• • In some countries, a maximum statute of limitations is established, considering even the effects of any suspension or interruption that may result from international requests for information.
• • Some tax codes stipulate that if an information exchange process exceeds a reasonable period (e.g., 2 years), the suspension ceases to have effect
• • If a taxpayer fails to report foreign assets, some countries (e.g., the U.S. and the U.K.) disregard the statute of limitations and its rules, allowing the tax authority to act at any time until the information is submitted.

Without clear rules on the calculation of time limits, international cooperation may lose its effectiveness as a tax enforcement tool, affecting both the government’s ability to collect taxes and taxpayers’ legal certainty

This post highlights the importance of deadlines in the field of international cooperation and the need to review and, where appropriate, modernize tax codes and procedures.

References:

CIAT, 2006. CIAT Manual for the Implementation and Practice of Information Exchange. General and Legal Aspects of Information Exchange. CIAT. https://www.ciat.org/Biblioteca/DocumentosTecnicos/Espanol/2006_Manual_CIAT_implantacion_Intercambio_Informaciones.pdf

CIAT, 2015. CIAT Model Tax Code: An Approach Based on Ibero-American Experience. https://www.ciat.org/Biblioteca/DocumentosTecnicos/Espanol/2015_Modelo_Codigo_Tributario_CIAT.pdf

Standards and documents on transparency and exchange of information from the Global Forum on Transparency and Exchange of Information for Tax Purposes. https://www.oecd.org/en/networks/global-forum-tax-transparency.html

Convention on Mutual Administrative Assistance in Tax Matters.

References:

[1] According to the CIAT Model Tax Code (CIAT, 2015), interruption means that the statute of limitations period starts running again from the beginning, without taking into account the time that had already elapsed. Interruption may occur as a result of notification actions related to tax collection, audits, inspections, or tax assessments. It may also occur when the taxpayer expressly acknowledges the tax liability or requests a tax refund or offset. On the other hand, suspension means that the statute of limitations period is temporarily paused for a specific period of time. Once the suspension period ends, the statute of limitations resumes running for the remaining time. Suspension may occur when a tax audit is initiated, an administrative appeal is filed, a claim is brought before the courts, or the tax administration is prevented from acting due to legal reasons or force majeure.

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