The RFB/CGIBS Joint Act No. 4 dated July 30 was published in the Diário Oficial da União on July 31 and entered into force on the day of publication. The document fixed the calendar of mandatory allocation of new taxes in electronic fiscal documents.
The first wave begins on August 3rd. From this date, companies in the normal mode are required to fill in the IBS and CBS fields in four documents: NF-e (Model 55), NFC-e (65), CT-e and MDF-E. The test rate is 1% in total, 0.9% for CBS and 0.1% for IBS, accrual in 2026 is informative and does not create tax consequences. The effect arises from the facts that have occurred since August 3.
The second wave falls in autumn. Starting from October 1, NFS-e with IBS and CBS details becomes mandatory for services subject to ISS according to the list of Additional Law No. 116/2003. Starting from December 1, separate situations and operations of digital platforms are added to it, as well as NF-e for IBS and CBS payers who are not ICMS payers.
The third wave is January 1, 2027. By this date, companies will switch to Simples Nacional, single-phase taxation operations, and imports of tangible goods, including Duimp. Effective collection of taxes under Supplementary Law No. 214/2025 begins on the same date.
By a separate clause, the act obliges RFB and CGIBS to publish a compliance program for 2026 for the transition period within 30 days.
The practical risk lies in validation. The tax service stated that it does not expect to fine this year, but experts warn of operational congestion: incorrectly filled in fields mean the rejection of the document, and with it the shipment.
What a business should do. For regular mode companies, check today that ERP and document submission systems generate IBS and CBS fields for all four types of documents. Exporters and importers working with Brazilian contractors should clarify the partners' readiness: a rejected NF—e or CT-e stops the shipment. Payers of Simples Nacional and importers have a reserve until January 2027, but the layouts for their documents should be put into operation now.
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