SIMPLES NACIONAL AND THE TAX REFORM: WHAT BUSINESSES NEED TO KNOW ABOUT THE NEW DEADLINES FOR 2027

A Tax Overhaul Directly Affecting Small Businesses

The Brazilian tax environment is undergoing one of the most profound transformations in its history. The Tax Reform, approved through Constitutional Amendment No. 132/2023 and regulated by Complementary Law No. 214/2025, completely redesigns the taxation of consumption in the country. Against this backdrop of structural change, entrepreneurs and managers of micro and small enterprises face a concrete challenge: understanding how the Simples Nacional and the new taxes, the Tax on Goods and Services (IBS) and the Social Contribution on Goods and Services (CBS), will coexist during the transition period.

In April 2026, the Simples Nacional Management Committee (CGSN) published Resolution CGSN No. 186, which establishes specific deadlines and conditions for the option to join the Simples Nacional for the 2027 calendar year and for adherence to the regular assessment regime for IBS and CBS. This is a high practical impact regulation, approved unanimously at the 70th in-person CGSN meeting, which requires immediate attention from business owners. Understanding its implications can make the difference between a smooth transition and unnecessary tax costs.

The Reform Context: IBS, CBS and the Simples Nacional

To understand the relevance of Resolution CGSN No. 186, it is necessary to place the issue in the context of the Tax Reform. The new model provides for the gradual replacement of five existing taxes, including PIS, Cofins, ICMS and ISS, with two new ones: the IBS, of shared competence between states and municipalities, and the CBS, of federal competence. The transition will take place gradually between 2026 and 2032, a period during which the old and new taxes will coexist.

For companies that opt for the Simples Nacional, this process generates additional complexity. The simplified regime consolidates, in a single collection document, all taxes owed by the company, including, until now, the contributions that will be replaced by the IBS and CBS. From 2027, the Simples Nacional will need to adapt to the new tax architecture, and companies will have to decide in advance how they wish to calculate and collect the new consumption taxes.

The Advance of the Option Period: September 2026

One of the main innovations of Resolution CGSN No. 186 is the advancement of the option period for the Simples Nacional for the 2027 calendar year. Unlike previous years, when the option is exercised in January, the regulation establishes that the formalization must take place between September 1 and 30, 2026, through the Simples Nacional Portal, with effect from January 1, 2027.

This advancement is not arbitrary. It stems from the need to align the simplified regime with the implementation of IBS and CBS, which will be fully applied from 2027 onwards. By knowing in advance which companies will be in the Simples Nacional, the government can properly structure the calculation and collection systems for the new taxes, providing legal certainty throughout the process.

From a business perspective, this advancement represents a tax planning opportunity. Managers will have, in the months preceding September 2026, sufficient time to analyze whether remaining in the Simples Nacional is economically advantageous given the changes brought by the reform, considering factors such as the sector of activity, the supply chain and the structure of tax credits.

The Option for the Regular IBS and CBS Regime: Flexibility in the Transition

Resolution CGSN No. 186 also introduces a relevant innovation: the possibility for companies opting for the Simples Nacional to choose, on an exceptional basis, the calculation and collection of IBS and CBS under the regular regime, applicable exclusively to the period from January to June 2027. This option must be exercised during the same period as the Simples Nacional option, that is, between September 1 and 30, 2026.

Choosing the regular IBS and CBS regime does not imply the taxpayer's exclusion from the Simples Nacional. In practice, the company will continue to collect all other taxes under the simplified regime, but the portions relating to IBS and CBS will be calculated and collected according to the general rules of the new tax system. This optionality offers companies an adaptation and testing period for the new regime, without giving up the advantages of the Simples Nacional for the other taxes.

For certain segments, especially those operating in production chains where purchasers are regular regime taxpayers, this possibility may be economically favorable. This is because, under the regular regime, the IBS and CBS allow for the calculation of tax credits, which can make the company more competitive vis-a-vis its buyers. The decision, therefore, requires careful analysis of the value chain and the specific characteristics of each business.

Cancellation of the Option and Deadline for Regularization

The regulation preserves mechanisms to protect taxpayers in the event of changes in circumstances. Both the Simples Nacional option and the regular IBS and CBS regime option may be irrevocably cancelled by the last day of November 2026. This deadline grants the company a revision window of approximately two months after the formalization of the option, a period during which changes in revenue, in the corporate structure or in market conditions may occur that justify reconsideration.

The resolution also provides that, if the Simples Nacional option is denied, the company will have up to 30 days to regularize any impeditive pending issues, counted from the date of notification of the denial. If the pending issues are regularized within this period, the denial will be cancelled and the option will be approved. This provision prevents irregularities that can be quickly resolved, such as tax debts in the process of installment payment or settlement, from definitively preventing adherence to the simplified regime.

This is a guideline aligned with the spirit of Complementary Law No. 123/2006, known as the National Statute of the Micro and Small Enterprise, which enshrines differentiated and favorable treatment for micro and small businesses as a constitutional principle set forth in Article 179 of the Federal Constitution.

Rules for Newly Established Companies

Resolution CGSN No. 186 establishes specific rules for companies incorporated between October 1 and December 31, 2026. For these companies, the exceptional deadline system of September does not apply. The option exercised at the time of CNPJ registration for the Simples Nacional will take effect from the registration date and for the entire 2027 calendar year. The option for the regular IBS and CBS regime will take effect for the months of January to June 2027.

This differentiation ensures equal treatment between already operating companies and those that will start their activities in the last quarter of 2026, avoiding regulatory gaps that could create legal uncertainty. For entrepreneurs planning to open new companies during this period, it is essential to be aware of these rules and to guide the corporate incorporation process accordingly.

It is important to note that the resolution does not apply to the System of Monthly Fixed Amount Collection of Taxes covered by the Simples Nacional (SIMEI), intended for the individual microentrepreneur. For MEI, the specific rules already established in their own regulations are maintained, which preserves the simplification that characterizes this regime.

Practical Implications for Corporate Tax Planning

From a strategic standpoint, Resolution CGSN No. 186 places managers of small and medium-sized enterprises before decisions that must be made based on concrete data about the reality of each business. The September 2026 deadline is not far away, and the period for adequate analysis begins now.

Among the relevant variables for the decision, the following stand out: the company's revenue volume and its potential approach to the Simples Nacional enrollment limit of R$ 4.8 million per year; the profile of the company's clients, considering whether they are end consumers or regular regime IBS and CBS taxpayers; the nature of the inputs used in the activity and the possibility of utilizing tax credits in the regular regime; and the company's cost structure compared to the tax rates provided in the Simples Nacional tables for each sector of activity.

A joint analysis of these factors allows the entrepreneur to make the most appropriate decision for their business reality, minimizing tax risks and maximizing the company's tax efficiency in the new scenario.

Early Planning as a Competitive Advantage

The publication of Resolution CGSN No. 186 is a clear signal that the transition to the new Brazilian tax system is advancing at a concrete pace. For entrepreneurs and managers of micro and small enterprises, ignoring these changes can mean loss of competitiveness, an increase in the effective tax burden and, in more serious cases, tax irregularities resulting from inadequate classification.

The key to navigating this process safely lies in early planning. The September 2026 window may seem distant, but the tax analysis needed for a well-founded decision requires time, data and specialized knowledge about the particularities of each sector and each company. Companies that begin this process early will be in a position to explore the opportunities that the new system offers, such as the possibility of utilizing IBS and CBS credits under the regular regime.

In this context, specialized legal and tax advisory services play a fundamental role. The Tax Reform, although representative of a necessary structural advance for Brazil, introduces a level of regulatory complexity that demands qualified technical interpretation. Decisions made without proper grounding can generate tax liabilities that compromise the financial health of the business. Seeking professional guidance before the September 2026 deadline is, therefore, a measure of prudence and business intelligence.