NFS-e with IBS and CBS from October 1: what your system needs to change

Starting October 1, 2026, most services subject to ISS (Brazil’s municipal service tax) must report IBS and CBS, the two new consumption taxes created by the tax reform, on the NFS-e, the electronic service invoice. The date is set by Joint Act RFB/CGIBS No. 4/2026, and most of what has been written about it targets accountants or users of off-the-shelf ERPs: "update your system" and that is it.

This article is for the other side: companies that issue invoices from a custom system, from an old ERP nobody updates anymore or through an integration built years ago. We cover which groups go into the DPS, where the calculation happens, how to test before going live, how to run both regimes side by side without stopping billing, and who is liable when something goes wrong.

Important: this text covers the technical side of the system. Tax classification, framing and regime are tax decisions: it does not replace advice from your accountant.

What changes on October 1 (and what waits until December and January)

The joint act does not switch every service on the same day. It splits by type of supply and by tax regime. The table below summarizes the dates that matter for NFS-e issuers:

Some context: 2026 is a test year. Complementary Law 214/2025 sets CBS at 0.9% (art. 346) and IBS at 0.1% (art. 343) for this year, offsettable against PIS and Cofins (art. 348). And art. 348, § 1 waives payment for those who meet their ancillary obligations. A correctly filled invoice is one of them. In short: the 2026 tax is small, but the data on the invoice is no minor detail.

"Not rejected" is not the same as optional: the non-compliance risk

The line you hear most is that "until December, an invoice without IBS and CBS goes through". True, but incomplete. The NFS-e Management Committee wrote that missing this information until December 31, 2026 will not lead to rejection by the national system, and in the same guidance said the omission shows the invoice is non-compliant, subjecting the issuer to the penalties and deadlines set in the joint act.

There is a second detail that trips up rushed integrations. The technical note that introduced the new groups explains that only the mandatory-presence rule was suspended. If the system sends the IBS and CBS group, its content is validated normally. In practice: sending nothing passes; sending it wrong may be rejected. Whoever turns on the new layout without testing trades a silent non-compliance for rejected invoices in the middle of billing.

What data the system needs to produce

In the national standard NFS-e, your system does not build the whole invoice. It sends the DPS (Service Provision Declaration) and the national environment returns the NFS-e, with part of the fields calculated by the platform itself. That changes what your code is responsible for. The specification is in the tax reform technical notes on the NFS-e portal and in the spreadsheet annexes that come with them.

What your system declares in the DPS

• IBSCBS group, with the purpose of issuance (finNFSe: regular, credit or debit invoice) and the personal use or consumption flag (indFinal).
• Operation indicator code (cIndOp), from a table published as an annex and based on art. 11 of LC 214/2025, which deals with the place of the operation.
• CST and cClassTrib (IBS/CBS tax situation code and tax classification code), inside the taxes group. This is where the operation is tied to the legal provision that defines its treatment.
• Recipient, when whoever receives the service is not the same party who pays (the dest group and the parties indicator).
• Conditional groups, case by case: presumed credit, deferral, regular taxation, real estate operations, movable property rental and government purchases.

What the platform returns in the NFS-e

The IBS and CBS place of incidence, the configured state, municipal and federal rates, the tax base, amounts and totals. Your system needs to read this response and store it, because that is what feeds finance, the accountant’s report and reconciliation. Two points of the formula deserve a developer’s attention:

• In 2026, the IBS and CBS base deducts ISS, PIS and Cofins; the technical note already sets the 2027 onward formula without PIS and Cofins.
• In 2026 the invoice total equals the net amount. From 2027, the technical note adds CBS and IBS to the total, since they are charged on top of the price. Bank slips, collections and reconciliation that rely on the invoice total will feel this change.

Technical Note 009: what is already on the horizon

NT SE/CGNFS-e No. 009 (version 1.0, June 4, 2026) brings changes that affect the database and screens, not just the XML: CNPJ (company tax ID) fields change from numeric to character because of the new alphanumeric CNPJ; credit and debit adjustment invoices are added; the base deduction and reduction groups were merged; Simples Nacional got its own fields (IBS/CBS calculation regime and activity code); and a group was created to link the invoice to the payment transaction (bank slip, Pix, wire transfer). The portal itself said the rollout schedule for this note would be published later, so check its current status before coding.

Where the calculation lives in your system

The most important decision is not about code, it is about master data. Each service you sell needs a classification (national tax code, NBS, operation indicator, CST and cClassTrib) defined with the accountant and stored as a parameter, per service and, where relevant, per customer type. The portal published a correlation table between item, NBS, operation indicator and cClassTrib, but warned it is a guide. Classification hard-coded in the source is what forces a development ticket every time a rule changes.

Custom system, market ERP or third-party issuer: who adjusts what

First, find out where your invoice goes. Since January 1, 2026, under art. 62 of LC 214/2025, municipalities must authorize issuance in the national environment or, if they keep their own issuer, share invoices in the standard layout with the national data environment. That defines who your system talks to.

Custom system

The work is all yours: data model (tax parameters per service, alphanumeric CNPJ), building the DPS with the new groups, reading and storing the response, a screen for billing staff to review before issuing, and reports. If the system talks to the city’s web service, confirm with the city which layout it accepts and since when. It is the scenario with the most work and the most control: you can test exactly your own cases.

Market ERP

The vendor updates the layout, but your company fills in the classification master data. Ask in writing: which version meets the October 1 date, whether it already issues in staging with the IBSCBS group, whether alphanumeric CNPJ is planned and what happens to your customizations (reports, finance integration) after the update. An old ERP without an active maintenance contract is the highest-risk case: it may simply never get the update.

Third-party issuer or invoicing API

Many companies issue through an intermediary service that takes a JSON payload and generates the invoice. The intermediary adjusts the layout, but your system is still the one sending the data. If the API contract gained new fields (classification, recipient, operation indicator), your code has to send them.

If you are deciding between adapting the current system or replacing it, our comparison of custom vs ready-made systems helps weigh both options.

Test plan before issuing in production

The national environment has Restricted Production, which the documentation itself calls the staging and testing environment. Invoices issued there have no legal validity. Use it.

1. Inventory. List the services you bill, the cities you issue from and your customer types (company, individual, government body, foreign).
2. Validated classification. Take the list to your accountant and record each service’s classification before writing a line of code.
3. Parameters. Store the classification as master data, with an effective date. Tax rules change; the invoice history must not change with them.
4. Staging test cases. A standard service; a customer in another city; an unconditional discount; a recipient different from the payer; cancellation and replacement; and every service with its own December date.
5. Check the response. Compare the returned base, rates and amounts with what the accountant expects. Keep the authorized XML.
6. Impact on the rest of the system. Do bank slips, receivables, reports and accounting integration still read the same fields? Simulate the 2027 total as well.
7. Gradual rollout. Turn on the new group per service or per customer, with a switch that lets you roll back, and watch rejections in the first days.

Who is liable when the invoice is wrong

Before the tax authority, the service provider issues the invoice. The Management Committee guidance refers to subjecting "the issuer" to penalties. Between the company, the accountant and the system vendor, the split depends on what was agreed: as a rule, the accountant guides the classification, the vendor answers for what the system does with the data and the company answers for the master data it keeps. Put it in writing now, before the first problem, and keep a record of who approved each classification.

And what comes in 2027

October is only the start. On January 1, 2027, Simples Nacional companies come in. Under LC 214/2025, CBS is charged at the reference rate reduced by 0.1 percentage point (art. 347) and IBS at 0.05% state and 0.05% municipal in 2027 and 2028 (art. 344). On the invoice, the total starts adding both taxes.

The next step is split payment: art. 31 of LC 214/2025 provides that payment service providers segregate and collect IBS and CBS at the moment of financial settlement, linking the tax document to the payment transaction. The payment link group in NT 009 already points that way. For legacy systems, we cover this in legacy systems and the tax reform; the banking side of the integration is in our PIX, Open Finance and ERP checklist.

"Until December 31, an invoice without IBS and CBS is authorized. But it is recorded in the national environment as non-compliant, and the issuer is you."

Conclusion

The October 1 change is small in tax and large in master data and integration. The no-rejection window until December is not slack to postpone the work: it is the window to test calmly, because 2027 brings Simples Nacional, taxes added to the invoice total and, further ahead, split payment.

Companies with custom systems or old ERPs have the advantage of controlling their own tests. Use Restricted Production, store the classification as a parameter and agree with your accountant on who decides what. If you need help on the system side, that is what we do in custom web systems, or reach us through the contact page.

Frequently asked questions

Do Simples Nacional companies need to report IBS and CBS on the NFS-e now?

Under Joint Act RFB/CGIBS No. 4/2026, the obligation for Simples Nacional companies starts on January 1, 2027. There is an earlier date, though: since November 1, 2026, micro and small companies under Simples must issue NFS-e through the National Issuer, on the web or via API (CGSN Resolution No. 191/2026). If your company issues from a custom system, the integration with the national API has to be ready by then. Confirm your case with your accountant.

Is an invoice without IBS and CBS rejected?

Until December 31, 2026, no: missing groups do not lead to rejection by the national system. But after each service’s mandatory date, an invoice without them is non-compliant and the issuer is subject to penalties. And note: if the group is sent, its content is validated, so wrong data may be rejected.

My city joined the national NFS-e. Now what?

Under LC 214/2025 (art. 62), since January 1, 2026 cities must authorize issuance in the national environment or, if they keep their own issuer, share invoices in the standard layout. If your city uses the national environment, your system should integrate with the national API and follow the technical notes on the NFS-e portal. If it uses its own issuer, confirm with the city which layout its web service accepts.

Who is liable for errors, the accountant or the system?

Before the tax authority, the issuer, that is, your company, answers for the invoice. Between the parties, it depends on what was agreed: usually the accountant guides the classification and the vendor answers for how the system works. Put it in writing and record who approved each classification.

Will I pay extra IBS and CBS in 2026?

LC 214/2025 sets CBS at 0.9% and IBS at 0.1% for 2026, offsettable against PIS and Cofins, and waives payment for those who meet ancillary obligations (art. 348). That is why a correctly filled invoice matters more than the amount. How it affects your own tax calculation is a question for your accountant.