Monthly and quarterly data series

The ABS will publish the first complete monthly measure of the CPI for the October 2025 reference period on Wednesday, 26 November 2025. This release will mark the beginning of the new Monthly CPI publication. 

The Monthly CPI data series and the new suite of monthly analytical series, including the monthly Trimmed mean, will go back to April 2024, coinciding with the point when the ABS increased the frequency of price collection.  

Table 1 presents the original data series that will be available in the Monthly CPI release. Table 2 outlines the analytical series. To support user readiness ahead of the complete Monthly CPI release, mock data tables that illustrate the format, structure, and content of the files will be published in September 2025. This resource will enable users to familiarise themselves with the layout of the data, variable naming conventions, and file specifications, so that systems can be updated ahead of the first release.

Original quarterly series  

The ABS will continue to produce a quarterly CPI data series (calculated as the average of the three relevant Monthly CPIs) to support those needing quarterly CPI figures for indexation, contract or other purposes. For information on which series this includes, see Table 1 above. The linked information paper outlines a range of issues that users should consider in relation to using price indexes in contracts - Inflation and Price Indexes - Use of Price Indexes in Contracts (abs.gov.au).

As part of the transition, some existing quarterly price indexes will be discontinued. Guidance will be provided on how users can construct quarterly indexes using the Monthly CPI series with the first release of the complete Monthly CPI.

Selected quarterly indexes on pre-October 2025 basis 

An appendix with selected quarterly seasonally adjusted and underlying inflation measures will be published in December, March, June, September monthly publications. This appendix will include:

These measures will continue to be compiled based on the pre-October 2025 collection frequency, preserving established seasonal patterns and quality while the monthly time series matures. The ABS will produce these legacy quarterly series for at least 18 months and are expected to be discontinued (by mid-2027), once sufficient monthly data exists for full standard seasonal adjustment approaches to be applied to all series. For further details see Seasonal adjustment for the new complete Monthly Consumer Price Index.  

The previously published quarterly index will be re-referenced and aligned to the new monthly series. This process will create a continuous historical time series for the quarterly CPI. While the levels of the quarterly CPI index will change due to re-referencing, the percentage movements of the index will not be revised. Any changes to movements will be due to rounding and a result of re-referencing. This does not constitute a revision. 

The reference period is the period for which the CPI index equals 100.0. The current reference period for the quarterly CPI is the 2011-12 financial year. The new quarterly index will be referenced to September month 2025, see example below. Re-referencing the historical quarterly series is a critical step in ensuring consistency between the historical and new quarterly series. 

September 2025 will serve as the link period where the index will equal 100.0. A conversion factor will be applied to adjust index values in the periods prior to September 2025. This adjustment resets the index levels while preserving the underlying quarterly movements.

The re-referenced quarterly indexes will be published for the first time in the December 2025 CPI release, scheduled for publication on Wednesday, 28 January 2026.

Example using mock data:

Learn more about re-referencing and linking price indexes for the Consumer Price Index.