Microsoft's September 2026 Power BI update is one of the largest of the year. Much of it is about AI, but there are also practical changes every report builder will notice. Here are the highlights, with what is generally available (GA) and what is still in preview.
For DAX and modelling
APPROXIMATEDISTINCTCOUNT for Import and Direct Lake (preview)
Counting distinct customers, orders or devices over hundreds of millions of rows can be slow. The new function trades a little precision for speed, with a standard error of about 1.6%.
Approx Customers = APPROXIMATEDISTINCTCOUNT ( Sales[CustomerID] )Use it for large trend visuals and dashboards where "about 1.2 million customers" is good enough, and keep DISTINCTCOUNT where numbers must reconcile exactly, such as finance reports.
Full-text search in DAX (preview, rolling out)
Two new functions, TEXTCONTAINS and TEXTSIMILARITY, search inside text columns, for example finding product descriptions or comments that mention a word, with a new string index to keep it fast. They need the latest model compatibility level, so check before relying on them.
Visual calculations for small multiples (GA)
Visual calculations, the simpler way to write running totals and comparisons directly on a visual, now work with small multiples. New to DAX? Start with DAX CALCULATE, explained and keep the DAX cheat sheet open.
For report builders
- Export to Excel up to 500,000 rows (GA), up from 150,000. Fewer "please send me the raw data" requests that need a workaround.
- Design ribbon with Dark and Soft dark themes (GA), for reports that look good on big screens and at night.
- Set and reset column widths in tables and matrices (GA), plus sticky format pane headers and an initial scroll position for axes.
- A new report ribbon on the web and improved on-object editing (preview).
- A new Power Query editor (preview) with a modern Get Data experience, query plans and a diagram view.
For teams and developers
- Power BI Projects (PBIP) is GA, and the PBIR report format is now the default. Reports and models are saved as readable text files, which means proper version control in Git, code review and less "final_v7.pbix".
- TMDL is available for semantic models, a readable text format for tables, measures and relationships.
- DirectQuery semantic models in the Power BI service, including composite models on the web.
AI and Copilot
- Agentic experiences (GA): AI agents can edit semantic models and reports through the Power BI Authoring MCP server.
- Copilot access control: model editors can stop read-only users from using Copilot and MCP on a semantic model.
- Power BI answers in Microsoft Copilot Chat are GA, and a Microsoft 365 Copilot entry point is in preview.
The practical advice is the same as ever: AI answers are only as good as the model underneath. Clear table and column names, descriptions and a clean star schema make Copilot far more reliable.
Dates to note
- October 2026: Power BI Desktop versions from March 2026 or earlier can no longer save or share files to OneDrive or SharePoint. Update Desktop if you are on an old version.
- Q&A: Microsoft is deprecating the classic Q&A feature. If any reports rely on Q&A visuals, plan to replace them.
Source: Microsoft's "Power BI September 2026 Feature Summary". Preview features can change before general availability, and some roll out gradually by region and tenant.
Alessandro Ecclesie AgazziWritten by Alessandro Ecclesie Agazzi, analytics engineer in London. Updated 13 October 2026. About me