New DAX UDFs – Create User Defined functions in Power BI DAX – Sep 2025 new Update

The September 2025 Power BI update introduces one of the most exciting features yet: User Defined Functions (UDFs) in DAX! 🎉

In this tutorial, I’ll show you step by step how to enable UDFs in Power BI Desktop and how to use them to write cleaner, reusable DAX code. With UDFs, you can stop rewriting the same long formulas and instead define them once and reuse them across multiple measures.

We’ll go through three practical examples that every Power BI user will find useful:

1️⃣ Add Tax Function in Power BI – Learn how to create a DAX UDF that automatically adds a percentage (e.g., 10% or 20%) tax or markup to measures. This is perfect if you frequently calculate Sales with Tax or Freight with Tax and want consistent, reusable logic. (Keyword: Power BI add tax measure)

2️⃣ Lifetime to Date / Cumulative Total Function – Build a DAX UDF that calculates a running total (also known as Sales LTD or cumulative sales). You’ll see how this works with filter context to give you a Power BI cumulative total across years or any time period. (Keywords: Power BI running total, Power BI cumulative sum)

3️⃣ Customers in Age Bracket Function – Create a UDF to calculate the number of customers in any age range (e.g., 40–60 years). This example shows how to handle parameters, row context, and filtering, making it a great approach for Power BI age calculation or demographic analysis. (Keywords: Power BI calculate age, Power BI age group analysis)

By the end of this video, you’ll see how UDFs make your Power BI models easier to maintain, reduce repetitive DAX code, and allow you to create powerful reusable calculations.

⚠️ Note: DAX UDFs are currently available only in Power BI Desktop and are not yet supported in the Power BI Service.

If you’re learning Power BI, DAX, or data modeling, this is a must-watch tutorial to stay ahead of the curve.

🔔 Don’t forget to like, share, and subscribe for more tutorials on Power BI, DAX, and the latest Microsoft updates.

⭐Download Example files:
https://excel-bonanza.kit.com/6330f0ec1b

Learn more about UDFs:
https://learn.microsoft.com/en-us/power-bi/transform-model/desktop-user-defined-functions-overview

https://www.sqlbi.com/articles/introducing-user-defined-functions-in-dax/

Chapters:
00:00 Introduction
00:50 How to enable/activate UDFs in Power BI
01:32 Example 1: Creating a UDF DAX function to add tax to an amount/measure
07:00 Example 2: Creating a UDF DAX function to calculate the Life time to date – LTD – Cumulative total value of a measure
11:10 Example 3: Creating a UDF DAX function to calculate the number of customers in a certain age bracket (Customers between 40 and 60 years old for example)
20:30 Conclusion and UDF Downsides and limitations

⭐Check out my Courses:

Power BI Dashboards Course:
https://abdelrahman-s-site-cb54.thinkific.com/courses/PowerBI-Dashboards

ExcelBonanza.com/Courses

Follow us on Social Media:
Facebook: https://www.facebook.com/ExcelBonanza
Twitter: https://twitter.com/ExcelBonanza
Follow me on Linkedin: https://www.linkedin.com/in/abdelrahman-abdou-60240150/
Instagram: https://www.instagram.com/excelbonanza1
TikTok: https://www.tiktok.com/@excelbonanza
Telegram: https://t.me/ExcelBonanza
Website: https://www.ExcelBonanza.com

#powerbidashboard #powerbiproject #powerbi_training #powerbitraining