Simplified Income Tax and Pre-Merger Review: Two Changes Worth Keeping on Your Radar

I. Decree 1253/2026: What Changes in the Simplified Income Tax Return

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1. What's New

Decree 1253/2026 replaces the regulations for the simplified Income Tax return regime (which had been approved by Decree 93/2026). It adapts it to Law 27,826 (known as “Fiscal Innocence II”), which amended Law 27,799. It entered into effect upon publication and entrusts ARCA with issuing supplementary regulations. On that basis, ARCA issued General Resolution 5916/2026 (Official Gazette of October 26). Among other provisions, that resolution eliminated the income and net worth caps that restricted access to the simplified modality. In addition, by means of General Resolution 5918/2026 (Official Gazette of October 30), ARCA extended the deadline to file Income Tax returns for the 2025 tax period for individuals and undivided estates, under both the general and simplified regimes, until November 16, 2026. According to its recitals, the extension addresses the impact of Law 27,826, Decree 1253/2026, and GR 5916 on the tax calculation for that period. The due date for the payment of the balance due, however, remains July 27, 2026.

2. Why It Matters

The simplified modality offers a key benefit. If the taxpayer files on time and pays the balance of the pre-filled return provided by ARCA, the filing has a full discharge effect regarding the period. Furthermore, the accuracy of the Income Tax and VAT returns for non-prescribed periods is presumed, admitting no evidence to the contrary. That protection lapses if ARCA detects a “significant discrepancy.” Therefore, the way the decree defines that concept is the cornerstone of the regime.

3. Main Aspects

a) When a significant discrepancy exists. A significant discrepancy exists when ARCA verifies any of the following situations:

• an increase in the assessed tax, or a reduction of the declared tax loss, of not less than 15% compared to what was filed;

• an increase in tax (or a reduction of the tax loss) that exceeds the threshold for basic evasion under Section 1 of the Criminal Tax Regime in effect at the return's due date. Under Law 27,799, that threshold is ARS 100 million;

• an adjustment arising from fraudulent invoices or from the improper calculation of withholdings, collections, advance payments, or installments. In these cases, a significant discrepancy exists regardless of the amount.

  
  

b) An amended return as a remedy. The difference will not be computed if the taxpayer amends their return within 15 business days of being served with the administrative assessment or ex officio determination, and pays or regularizes the balance along with accrued interest.

c) Lower statutory formal fines. The decree establishes two reductions for MSMEs, individuals, undivided estates, and non-profit entities, unless they are classified as National Large Taxpayers:

• a permanent 25% reduction (Section 49 bis of Law 11,683);

• a special 50% reduction (Section 17 of Law 27,826), subject to curing the omitted formal obligation within the deadlines and conditions set by ARCA.

The taxpayer's status is assessed at the time of non-compliance, and these reductions are compatible with other relief mechanisms provided under Law 11,683.

d) Who can use the regime. Resident individuals and undivided estates meeting legal requirements may opt in. Under GR 5916, National Large Taxpayers and certain public officials may file and pay through this procedure, but they do not obtain the discharge effect or the presumption of accuracy. GR 5916 further clarifies that the lack of banking channel usage in a transaction is not, in itself, a ground for exclusion.

e) Regime change for the 2025 period. Those who have already filed their 2025 Income Tax return under the general regime and meet the requirements may switch to the simplified modality. To do so, they must file an amended return before the expiration date for the simplified return, which GR 5918/2026 extended until November 16, 2026.

4. What We Recommend Reviewing

• Those who filed 2025 Income Tax under the general regime: evaluate before November 16, 2026, whether it is advisable to amend and switch to the simplified modality in light of the new rules.

• Evaluate on a case-by-case basis whether the simplified modality is convenient. The presumption of accuracy is valuable, but it requires that the pre-filled return be thoroughly reviewed.

• Pay special attention to the computation of withholdings, collections, and advance payments, as well as suppliers' documentation: for these, a significant discrepancy does not require a minimum threshold.

• In the event of an assessment or determination by ARCA, keep in mind the 15-business-day deadline to amend and preserve protection.

• In the case of MSMEs with pending formal fines, verify the automatic application of the reductions and, once ARCA establishes the conditions, cure the non-compliances to access the 50% reduction.

II. Mergers and Acquisitions. Prior Clearance Enters into Force on November 17.

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5. What's New

Since the enactment of the Antitrust Law 27,442 (2018), economic concentration control has operated under a transitional regime. Covered transactions are notified prior to closing or within the following week, and may be completed without awaiting the authority's decision. Section 84 of the law provided that the definitive system of prior and suspensive control (Section 9) would enter into force one year after the National Competition Authority (ANC) became operational. That term expires on November 17, 2026.

On September 18, 2026, the Antitrust Tribunal published in the Official Gazette a general interpretive guideline regarding the transition between both regimes.

6. Key Features of the New Regime

a) Notification and clearance prior to closing. Covered transactions must be notified and cleared before closing or the acquisition of control, whichever occurs first. Pending clearance, whether express or tacit, the transaction has no legal effect between the parties or towards third parties. Between notification and clearance, buyer and seller must continue operating as independent companies.

b) What transactions must be notified. Transactions deemed to be concentrations include the acquisition of control of one or more companies through mergers, transfers of ongoing concerns, acquisitions of shares or equity interests granting control or substantial influence, and other acts granting decisive influence over management or competitive strategy (Section 7). They must be notified when the total turnover in the country of the group of affected companies exceeds 100 million mobile units (Section 9).

c) Exemptions. Section 11 exempts, among other cases, the following transactions:

• acquisitions where the buyer already held more than 50% of the company, with no change in the nature of control;

• purchases of bonds, debentures, non-voting shares, or debt securities;

• first acquisition in the country by a foreign company without prior assets or equity holdings in Argentina (subject to certain conditions);

• acquisitions of companies with no business activity in the country in the last year, unless their activities overlap;

• transactions where neither the transaction value nor the value of assets located in Argentina exceed, individually, 20 million MU. The exemption does not apply if cumulative transactions in the same market exceed that amount in the preceding 12 months, or exceed 60 million MU in the preceding 36 months.

d) Thresholds in Argentine pesos for 2026. The mobile unit is updated annually. For 2026, it was set by Resolution 6/2026 of the Antitrust Tribunal (Official Gazette of 01/16/2026) at ARS 1,450.05. Key values are as follows:

e) Terms. Once complete information is submitted, the authority has 45 business days (administrative business days, as are all deadlines under the law) to clear, conditionally approve, or deny the transaction. If it identifies competition concerns, it may raise objections and extend the review period by up to 120 additional days. If the deadline expires without a decision, the transaction is deemed to be tacitly approved (Sections 14 and 15). Lower-risk transactions may be processed through a simplified procedure.

f) Penalties for failure to notify or early closing (“gun jumping”). Failure to notify a covered transaction, or taking control without approval, may result in fines of up to 0.1% per day of the group's consolidated national turnover. If that criterion cannot be applied, the cap is 750,000 MU per day. The fine accrues from the breach of the obligation or from the assumption of control (Section 55, subsection d). The authority may also order corrective measures, including divestiture or unwinding the transaction.

7. The Transition: The Notification Date Is Decisive

According to the Antitrust Tribunal's interpretation:

• transactions notified before 00:00 on 11/17/2026 remain subject to the transitional, non-suspensive regime, even if closing occurs thereafter;

• conversely, if the agreement predates that date but notification occurs on or after 11/17/2026, the prior and suspensive control applies;

• notification requires a legally binding agreement, executed by duly authorized representatives. Letters of intent, memoranda of understanding, term sheets, and non-binding offers are not sufficient. The fact that closing is subject to conditions precedent, such as other regulatory approvals, does not prevent notification;

• applying the transitional regime does not imply approval: the Tribunal retains all its powers, and a transaction closed prior to resolution is executed at the exclusive risk of the parties.

8. What We Recommend Doing

• Pending transactions. If a binding agreement is signed or close to being signed, urgently evaluate whether it is advisable to notify before 11/17/2026 to remain under the transitional regime.

• New transactions. Incorporate antitrust analysis from the outset of negotiations and include ANC clearance in the transaction timeline as a condition precedent to closing.

• Contracts. Review conditions precedent, long-stop date, interim covenants, and regulatory risk allocation clauses to avoid granting the buyer influence over the target prior to approval.

• Sensitive information. During negotiations and until closing, channel the exchange of competitively sensitive information through clean teams and confidentiality protocols.

• Groups with multiple acquisitions. Monitor the accumulation of transactions in the same market over the last 12 and 36 months, which may void the monetary exemption.

  
  

To evaluate the impact of these developments on your specific situation, please contact your regular firm representative.

This material is for general informational purposes only and does not constitute professional advice for specific cases.