Law No. 13.670 / 2018 has changed Article 74 of the Law No. 9.430 / 1996 which ends the practice of calculating the monthly IRPJ (capital gains tax) and CSLL (social security contributions) based on estimates of the tax base. Prior to the law change, numerous taxpayers went to court successfully fighting the new regulation which resulted in its suspension until the end of 2018.
However, the federal courts suspended the decisions in favor of the taxpayers arguing that they should have awaited the final version of the respective law.
In reaction to the law change, the Provisional Measure (MP) Nr. 836/2018 was granted by the Poder Executivo (president, governors or mayors). This MP includes change request which ultimately lift the prohibition of estimating the tax base. If the MP is passed in Congress and ratified by the president, tax payers have a legitimate chance of upholding the current calculation process.