CBS 2027 Reference Rate: The TCU-Senate Timeline Tax and IT Teams Must Monitor Through December

The missing number to close the CBS equation in 2027 is now in progress

While the tax market's attention remains focused on NF-e technical notes and split payment schedules, a decisive move in the Consumption Tax Reform is quietly advancing behind institutional scenes: the definition of the CBS reference rate that will replace PIS and Cofins starting January 1, 2027. This number, currently an official unknown, directly impacts the parameterization of tax systems, the pricing of products and services, and the adjustment clauses in current contracts.

What has already happened

(cite index="41-3">The federal government submitted the CBS rate calculation proposal to the Federal Court of Accounts (TCU) on September 14, 2026, with (cite index="41-4">the calculation proposal developed by the Federal Revenue Service, using a methodology prepared in collaboration with the court. This submission is not a mere bureaucratic procedure: it is the trigger that starts the legal clock for setting the percentage that will apply next year.

The timeline that still needs to be met

• (cite index="41-5">The TCU will have until October 30 to send the Federal Senate the calculations for the CBS reference rate, a deadline that (cite index="39-3">was exceptionally extended by 45 days this year, meaning the approved proposal must be sent to the Senate by October 30.
• (cite index="41-6">After receiving the figures from the TCU, the Senate must set the reference rate by December 15, and (cite index="41-7">the ninety-day prior notice rule provided for in the Federal Constitution does not apply to this deadline — meaning the percentage can take effect as early as January 1, 2027, even if defined just days before.
• There is also a safety clause: (cite index="43-4">if the Senate does not act within this window, the number calculated by the TCU itself will automatically take effect, a mechanism provided for in the legislation to prevent the new tax from reaching 2027 without a defined parameter.

The numbers already circulating (and why none of them is final)

The IBS Steering Committee has already published reference estimates, but they must be read with caution: (cite index="37-9">CGIBS resolutions estimated the total tax burden at 27.91% by the end of the transition in 2033, with the CBS share corresponding to 9.21%. The body itself makes the usual disclaimer: (cite index="39-4">the published estimate does not represent the final rate of the new tax system and may be adjusted as new fiscal, economic, and revenue-collection information becomes available.

For the year that actually matters to companies right now — 2027 — the scenario is more specific: (cite index="38-11">in 2027, only the 0.1% IBS test rate applies, and the CBS takes effect replacing PIS and Cofins, with the transition ending in 2033. Meanwhile, (cite index="41-12">the IBS reference rates will be set for the years 2029 through 2033, which reinforces that the process currently underway is, in practice, about the CBS percentage. Tax consultancies are already venturing projections: (cite index="41-15">tax technology company ROIT estimates that the CBS rate in 2027 will be 9.43%, while the projected legal reference ceiling for the combined IBS+CBS is around 26.5%. Broadly speaking, (cite index="44-12">market estimates range from 26.5% to about 28%, depending on the number of exceptions considered. To gauge the budgetary impact, it is worth noting that (cite index="41-13">the federal government projects collecting R$636.8 billion from the CBS in 2027.

Why this is already an IT and tax matter, not just something for September

Unlike a technical layout note, the reference rate does not arrive months in advance for validation in a test environment. The legal timeline allows the Senate to publish the resolution in December, with no constitutional waiting period, for it to take effect the following January. This means that fiscal document issuance systems, tax calculation engines, and pricing tables need to be ready to receive a new parameter with very little room for adaptation.

Practical recommendations for tax, accounting, and IT teams:

• Monitor the publication of the Senate resolution (expected by 12/15/2026) and avoid locking in the 2027 CBS rate in any final parameterization before then.
• Ensure that the ERP and tax calculation engine allow for quick, centralized updating of the CBS percentage as soon as the resolution is published, without the need for manual reprogramming in each operation.
• Review supply and service contracts with tax pass-through clauses, clarifying how any CBS variation will be absorbed or passed on.
• Align with the accounting team on the impact of the new rate on the margins of products and services already budgeted for the first quarter of 2027.

This content is for informational purposes only and does not replace guidance from your accounting team, which should assess the specific impact of the CBS reference rate on your business as soon as the Senate publishes the final resolution.

Want to keep your company's ERP ready for whatever rate scenario comes out of the Senate by December? Talk to Edoo and prepare your tax parameterization in advance.