Joint Act RFB/CGIBS No. 4/2026: The Definitive Timeline for IBS/CBS in Tax Documents, Document by Document

A new joint act changes the reform's deadline ruler

On Friday, July 31, 2026, the Brazilian Federal Revenue Service and the IBS Management Committee published Joint Act RFB/CGIBS No. 4, of July 30, 2026, which

The Federal Revenue Service and the IBS Management Committee published, on July 31, 2026, Joint Act RFB/CGIBS No. 4, establishing the official and detailed schedule for the mandatory issuance of electronic tax documents (DF-e) with the CBS and IBS fields. The act defining the new start dates for the mandatory issuance of electronic tax documents related to the Tax on Goods and Services (IBS) and the Contribution on Goods and Services (CBS) complements the existing legal basis, since the publication fulfills the commitment announced by the Brazilian Federal Revenue Service and the IBS Management Committee earlier this week and complements CGIBS Resolution No. 16/2026, which granted provisional authority to the President of the Management Committee's Superior Council to issue, jointly with the Brazilian Federal Revenue Service, the official schedule for the implementation of the tax documents.

For IT and tax teams, the practical message is straightforward: the rule is a significant milestone for accountants, tax analysts, and system developers, as it turns into concrete dates the adaptation process set out by Constitutional Amendment No. 132/2023 and Supplementary Law No. 214/2025.

What remains in effect on August 3, 2026

Despite all the buzz around a possible general postponement, the schedule confirms August 3, 2026 as the mandatory date for documents already consolidated in the market — NF-e, NFC-e, CT-e, CT-e OS, MDF-e, GTV-e, NF3e, DC-e, and NFS-e Via, among others. In other words, whoever issues these documents must ensure that the system is already configured with the IBS and CBS groups, under penalty of rejection in the production environment.

It's worth remembering why the government chose to stagger the process instead of keeping everything unified on a single date: the postponement was prompted by failures: 21% of the documents issued between June and July were sent without the CBS fields filled in. This data, gathered by the Revenue Service itself, shows that a significant portion of the market had not yet completed the certification of the new fields.

NFS-e gets its own, more gradual calendar

Unlike NF-e and NFC-e, the National Electronic Service Invoice receives more staggered treatment. According to the joint act, the NFS-e receives differentiated and more gradual treatment: most services (digital platforms, movable and real property rentals, condominiums, intangible assets, and other provisions) will only require the IBS/CBS breakdown starting December 1, 2026, while specific services also subject to ISS (subitems 1.03, 1.05 and 1.09) follow the same December date, and the remaining ISS-subject services not covered by these cases will require the fields starting in October. It is important to check the exact classification of the service provided, since the date changes depending on the subitem of the list in Supplementary Law 116/2003.

DeRE: new ancillary obligation also gets a schedule

The Declaration of Specific Regimes (DeRE), a new ancillary obligation under the reform, also has its own staggered rollout. According to the act, the obligation will be implemented gradually, starting on: October 1, 2026, for events related to the Taxpayer Table; November 15, 2026, for monthly periodic events; and January 1, 2027, for events not covered by the previous cases. In practice, Monthly Periodic Events must be submitted starting November 15, 2026, regarding information for the October 2026 assessment period, which requires that October's assessment already be correct even before the first formal submission.

Simples Nacional and other points of attention

For those operating under Simples Nacional, the deadline remains different: for taxpayers opting for Simples Nacional, the mandatory issuance of the tax documents covered by the act will begin on January 1, 2027. As for the Electronic Invoice for the Sale of Real Estate, a new model created by the reform, it is mandatory starting December 1, 2026.

Another point that deserves attention from tax teams: within 30 (thirty) days, a joint act from the RFB and CGIBS will be published establishing the compliance program for the issuance of tax documents for the year 2026. This program should detail how the remaining inconsistencies will be handled during this transition period — it's worth following closely.

Checklist for tax and IT teams

• Confirm whether the issuing system already validates the IBS/CBS fields for NF-e, NFC-e, CT-e, MDF-e, and other documents required starting 8/3.
• Map the classification of each service provided to determine whether the NFS-e falls under the October or December rule.
• If the company is a Simples Nacional participant, review whether any specific document already requires adjustment before January 2027.
• Stay alert for the publication of the 2026 Compliance Program, expected within the next 30 days.
• Test all scenarios in the certification environment before any new cutoff date.

This content is for informational purposes only and does not replace guidance from your accounting team or a specialized professional, who should assess your company's specific classification.

If your team is struggling to keep up with all these changes in your ERP, Edoo can help keep your tax processes on track. Talk to Edoo.