Simples Nacional 2027: September is decision month, and now you choose how to pay IBS/CBS

What changes in September 2026

Today, September 1, 2026, the window to opt into Simples Nacional (Brazil's simplified tax regime for small businesses) for 2027 opens, and it runs through September 30. For the first time, this request moves from January to the September before the year it applies to. And with it comes a new decision: how you will pay IBS and CBS.

The information comes from the Receita Federal (Brazil's federal tax authority), which published the notice on the opening day itself. The legal basis is Complementary Law 214/2025 and CGSN Resolution No. 186/2026, dated April 9, 2026 and published in the Diário Oficial da União (Brazil's official gazette) on April 17.

If your CNPJ (company tax ID) is already in Simples and nothing unusual has happened to it, you may not need to do anything. But "may" is an expensive word when it comes to tax, so it's worth understanding the full picture before ignoring the deadline.

A note on why this is changing. The Receita says the goal is to make the transition to IBS and CBS smoother and to give micro and small businesses predictability. It makes sense: if the choice of payment model has to exist before 2027 starts, the opt-in request also has to come earlier.

This article is for small-business owners, not accountants. I'll explain what changed, who needs to act, how to think through the choice between the two models, and what nobody can answer with confidence yet. At the end there's a checklist you can take to the conversation with whoever handles your accounting.

In one sentence, what are IBS and CBS

IBS and CBS are the new consumption taxes created by the tax reform. Over time, they will replace taxes you already know. For this article, all that matters is this: in 2027 they enter your routine, and how you pay them depends on a choice you make now.

This article doesn't get into tax rates or calculations, because the official sources consulted don't provide those numbers. When I say something isn't defined, it's because it isn't in the sources, not because I forgot to look.

Who needs to do something in September?

Not every company needs to act in September. Businesses already in Simples Nacional stay in it automatically, unless there is a future-exclusion record on their registration. Businesses that were excluded and have that record must request the opt-in within the window, September 1 to 30, 2026, according to the Receita Federal.

Let's break it down by situation, because the rule changes depending on your case.

Companies already in Simples

You don't need to file a new opt-in request. Staying in is automatic. The only caveat is the one I mentioned: if there is a future-exclusion record, the story changes.

How do you find out? Log into the Simples Nacional Portal during September and check your status. It's a five-minute check that avoids a surprise in January. If you don't have the access code or digital certificate at hand, ask your accountant to take a look.

And note this: even those who don't need to request the opt-in still have a decision ahead, which is the IBS and CBS model. I cover that in the next section.

Companies excluded with a future-exclusion record

Here the deadline is real. If your company left Simples, or is going to, and this record exists, the opt-in request must be made in September. Without it, the automatic-stay rule doesn't protect you.

This is the case where I see the most risk of forgetting, because people who were excluded are often tired of the subject and put it off. The deadline is now short and fixed, unlike previous years, when January gave a mental breather after the holidays.

CNPJs opened between October and December 2026

If you're opening a company now, the rule is simpler. Anyone who registers a CNPJ between October 1 and December 31, 2026 gets the opt-in at the moment of registration. It applies for the rest of 2026 and for the whole of 2027.

What about the MEI?

The MEI (Microempreendedor Individual, Brazil's solo micro-entrepreneur category) is not part of this change. The MEI opt-in stays in January, and there is no hybrid alternative for it. If you're an MEI, you can breathe easy: this article is about the other Simples company sizes.

If you're an MEI thinking about growing and becoming a microenterprise, it's worth talking to your accountant first. The deadline and the IBS/CBS model are part of that calculation.

What is the choice between "pure" and "hybrid" IBS/CBS?

The novelty for 2027 is that Simples Nacional now has two models for paying IBS and CBS. In the pure model, both taxes are paid inside Simples' single payment slip, the DAS. In the hybrid model, you stay in Simples for the other taxes, but pay CBS and IBS under the regular regime, outside the slip, according to the Receita Federal.

That sounds abstract, so let me translate it into day-to-day terms.

Pure model: everything on the same slip

In the pure model, nothing changes in how you pay. You keep a single slip, the DAS, and IBS and CBS come built into it. It's the path closest to what you do today.

The advantage is simplicity. One slip, one due date, a routine your team already knows. The possible drawback, which we'll see further on, depends on who buys from you.

Hybrid model: Simples for the rest, regular regime for IBS and CBS

In the hybrid model, your company stays in Simples Nacional for the other taxes. But CBS and IBS leave the single slip and are calculated and paid under the regular regime, that is, outside the DAS.

In practice, this means one more parallel obligation. You end up with two payment paths running at the same time: the DAS for what stayed in Simples, and the regular payment for CBS and IBS. That usually calls for a more organized routine and, almost always, more support from accounting.

Why the Receita talks about B2B

The Receita Federal points out that the hybrid model may be relevant for companies that sell to other companies, known as B2B. The reason cited is that these companies' customers may be able to use credits more broadly.

In plain English: when you sell to a business, it usually wants to offset the tax it paid on the purchase. The way you pay can affect how much it can offset. That can weigh on the commercial negotiation, which is why this isn't only a tax topic.

Notice the "may." The Receita doesn't say the hybrid is better for those who sell B2B. It says it may be relevant. The right choice, according to the agency itself, depends on the business.

Which model is worth more for your company?

There is no universal answer, and the official sources don't provide a cost comparison between the two models. The Receita Federal says only that the choice depends on the business and that the hybrid may matter for those who sell to other companies. So the way forward is to look at your customer profile and talk to your accountant.

You can organize the conversation around three simple questions.

Question 1: who do you sell to?

Split your revenue into two blocks: sales to end consumers (individuals) and sales to other businesses. The bigger the B2B block, the more the credits issue tends to matter.

The bigger the end-consumer block, the less that argument weighs, and the simplicity of the pure model tends to gain importance. I say "tends" because nobody can state the outcome without the numbers for your case.

Question 2: do your business customers ask for this?

Talk to your two or three biggest business (PJ) clients. Ask, plainly, whether the way you pay your taxes affects their purchase. Some will answer right away. Others will say they need to check with their own accounting, which is already a useful signal.

This conversation is worth more than any generic spreadsheet, because what the Receita describes is precisely how your customers behave with credits.

Question 3: can your operation handle two routines?

The hybrid takes IBS and CBS out of the single slip. That requires someone (you, an employee, or the accounting firm) to handle that calculation separately. If your tax routine is lean today, ask how much this would cost in hours or in fees.

A hypothetical example to fix the logic

Note: the example below is hypothetical, with round numbers made up only to illustrate the reasoning. They are not real data, nor tax rates, nor a tax estimate.

Imagine two companies, A and B, each with R$ 100 thousand in sales per month (illustrative value). Company A sells R$ 80 thousand to other businesses and R$ 20 thousand to end consumers. Company B sells R$ 10 thousand to other businesses and R$ 90 thousand to end consumers.

By the criterion the Receita mentions, Company A is the natural candidate to give the hybrid a serious look, because most of its customers are businesses that may be able to use credits. Company B has less reason to complicate its routine. Even so, only a calculation done with each company's real data says which model comes out better. The example shows the path of reasoning, not the result.

What the sources don't say

It's worth being honest about the limits. The sources consulted don't provide examples of tax rates, credit amounts, or an answer on which model is cheaper. They also don't provide an official count of how many companies are expected to choose each model.

If someone promises you a ready-made answer about "the best model" without looking at your customer mix, be suspicious. The answer depends on who buys from you.

What happens if I don't choose anything?

If you don't choose a model, the pure one applies. According to the Receita Federal, that is the default applied from January to June 2027. In other words, not choosing doesn't leave the company without a rule: it falls into the path closest to what you already do, with IBS and CBS inside the single slip.

That's a relief, but it doesn't solve everything. Choosing by default is also a decision, just one made without looking at your customers.

The period covered by the September choice

The choice made in September 2026 applies to the first half of 2027, January to June. It is not a decision for the whole year.

The next opportunity to choose comes in March 2027, and the decision made then takes effect in the second half of 2027. Thinking this way reduces the pressure: you're not locking the company into a model indefinitely.

But be careful with the hasty conclusion of "so it doesn't matter." Six months under a model that doesn't fit your customer base can be costly in margin or in commercial negotiation.

What if I miss the opt-in deadline?

Here I need to be direct: the sources consulted don't detail what happens to those who need to request the opt-in and let the window pass. That consequence isn't defined in the materials I used, so I won't make it up.

What I would do in your place: treat September 30 as a hard deadline and ask your accountant, in writing, what the company's situation is. If it's a future-exclusion case, treat it as urgent.

Can you go back? Cancellation and the March window

You can cancel, but under strict rules. According to the Receita Federal, cancellation is allowed until the last day of November 2026. Once canceled, the act is irrevocable and you cannot request the opt-in again for 2027. So cancel only if you are sure of what you're doing.

This rule deserves to be read twice, because it has a catch.

Cancellation is irrevocable

If you requested the opt-in and then canceled, there is no "undo the cancellation." Nor can you refile the request for 2027. The sources don't detail what comes after that, so ask your accountant before you click.

People thinking about canceling are usually comparing regimes. That's a legitimate comparison, but it needs to be done with a professional's simulation, not by guesswork. An irreversible decision like this deserves a second opinion.

Request denied due to pending issues: 30 days to regularize

If your request is denied because of a debt or another pending issue, the Receita gives you 30 days to regularize the situation. It sounds generous, but in practice the clock runs fast: identifying the issue, paying or installing the debt, and waiting for the system to reflect it.

That's why it's worth checking your debts and pending issues before requesting the opt-in, not after. If something is open, resolve it right away in September.

September checklist to take to your accountant

A good checklist turns the deadline into small tasks. The window runs from September 1 to 30, 2026, and the Receita Federal says that the opt-in, when accepted, takes effect on January 1, 2027. Those who get organized in the first week have time to fix any pending issue.

Use the list below as a conversation guide.

First week: find out where you stand

• Log into the Simples Nacional Portal and check whether there is a future-exclusion record.
• Check whether there are open debts or pending issues, federal, state, or municipal.
• Confirm who at the company has access to the portal (you, the accountant, or both).
• Note whether the company is an MEI. If it is, the September deadline does not apply.

Second and third weeks: decide the model

• Split the revenue of recent months between sales to businesses and sales to end consumers.
• Talk to your biggest business clients about the impact of how you pay.
• Ask your accountant for a simulation with your numbers, not generic ones.
• Ask how much it costs, in time and fees, to keep a parallel calculation of CBS and IBS.

Last week: register and keep records

• Make the model choice within the window, if it differs from the default.
• Keep a receipt or screenshot of the request and the result.
• Set a reminder for March 2027, when there is a new chance to choose.
• Note the November deadline, in case there is any doubt about canceling.

Common mistakes that can be costly

The most frequent mistakes are predictable: thinking a request is an approval, thinking that paying the debt fixes everything, and thinking the federal check is enough. These points don't come from statistics, but from the practical logic of how these processes tend to work.

Let's go through the ones that cause the most trouble.

Confusing a request with an approval

Sending the request is not the same as being accepted. The company may have pending issues that block the opt-in. Follow the result, not just the submission.

Paying the debt and forgetting the filing

Paying off a debt doesn't fix a return that wasn't filed. They are different problems, with different fixes. If you only paid the bill and the ancillary obligation is still open, the pending issue is still there.

Thinking the federal check is enough

The check done by the Receita doesn't replace the ones from states and municipalities. A company can be in good standing at the federal level and have a state or municipal pending issue. Ask your accountant to look at all three levels.

Deciding only by the price of the slip

It's tempting to pick the model that looks cheaper on paper. But the cheapest for you may be the most expensive for your business customer, if it affects their credits. And a customer who notices the impact may ask for a discount or switch suppliers.

Leaving everything for September 30

A last-day deadline is a gamble. The system may slow down, your accountant may have a full calendar, and a pending issue discovered at the end leaves no time to regularize. The earlier you look, the more options you have.

Treating the decision as only the accountant's

The accountant executes and advises, but you are the one who knows your customers. The choice of model depends on your sales mix and your commercial relationships. They need that information, and only you have it.

And the invoice with IBS and CBS?

The reform has also reached the invoice. According to material from Fenacon and Sebrae dated August 11, 2026, the testing period for the IBS and CBS fields on the NF-e and NFC-e (Brazil's electronic invoices) began on August 3. The test rate is 1% (0.1% IBS and 0.9% CBS), informational only.

For those in Simples, the obligation to comply with the new rules starts on January 1, 2027. The same source reports that the Receita and the CGIBS temporarily suspended the automatic rejection of invoices without IBS and CBS data.

This suspension is temporary, so don't treat it as permission to put it off. It's worth aligning with your invoicing system and your accountant, in parallel with the September decision. This topic deserves its own article, and here is just the context: the model choice and the invoice go hand in hand in preparing for 2027.

Quick questions

Do I need to request the Simples opt-in again if I'm already in it?

In general, no. Businesses already in Simples Nacional stay in automatically, according to the Receita Federal. The exception is a company with a future-exclusion record. Check your status in the Simples Nacional Portal during September, so you're not surprised in January.

What is the deadline, and when does the opt-in take effect?

The window runs from September 1 to 30, 2026. If the opt-in is accepted, it takes effect on January 1, 2027. This is the first time the request happens in September rather than January, according to the Receita.

Does the MEI also need to choose between pure and hybrid?

No. The MEI is not affected by this change. The MEI opt-in stays in January and there is no hybrid model for it. If you're an MEI, the September deadline does not apply to your business.

Which model is cheaper?

Nobody can say without looking at your numbers. The official sources don't provide a cost comparison between the models. The Receita says the choice depends on the business and that the hybrid may matter for those who sell to other companies. Ask your accountant for a simulation.

Can I change the model later?

Yes, partly. The September choice applies from January to June 2027. There is a new chance in March 2027, taking effect in the second half. Canceling the opt-in is a different matter: it is irrevocable and runs until the end of November 2026.

Is it worth waiting to decide?

Waiting until the last day only gets in the way. Pending issues discovered late leave little time to regularize, and a denied request only gives you 30 days. The ideal is to check your situation in the first week and use the rest of the month to decide calmly.

Where Diglion comes in

Diglion helps small and medium-sized businesses turn this kind of deadline into routine: mapping the customer base between B2B and end consumers, organizing revenue data for the simulation with the accountant, and preparing invoicing and financial management systems to work with the new IBS and CBS fields from 2027.

Sources consulted

• Receita Federal, Receita Federal alerta: começa hoje o prazo para opção pelo Simples Nacional e para a escolha do modelo de recolhimento do IBS e da CBS em 2027, retrieved 2026-09-01.
• Receita Federal, Prazo para solicitação pelo Simples Nacional será em setembro de 2026, retrieved 2026-09-01.
• Agência Gov, Prazo para solicitar ingresso no Simples Nacional passa a ser em setembro de 2026, em vez de janeiro, retrieved 2026-09-01.
• Fenacon e Sebrae, O que os pequenos negócios precisam saber sobre os novos impostos na nota fiscal, retrieved 2026-09-01.