Microsoft is retiring the =COPILOT() function, which let users call an AI model directly from an Excel cell, on September 14, 2026. The feature entered preview in August 2025 and will disappear without ever graduating to general availability. On the same day the retirement was announced, the roadmap entries for its planned launch were withdrawn as well, making this a cancellation of the feature rather than a change of schedule. Here is a look at why running AI inside a formula turned out to be an awkward fit for a spreadsheet.

Not a delay, but a withdrawal

On August 13, 2026, Microsoft used the Microsoft 365 Message Center to notify customers that Excel's =COPILOT() function would be retired on September 14. From that date the function is removed from Excel and can no longer be used in new formulas. No administrator action is required.

What stands out is that the roadmap was rewritten on the same day. Separate entries covered general availability for the Windows desktop, Mac, and web versions of Excel, each targeting worldwide rollout in January 2027. All three were replaced with wording stating that Microsoft has decided not to move forward with the feature. The plan was shelved roughly 5 months before the scheduled launch, with no replacement implementation or migration path offered.

In other words, this is not a pause in the preview or a reset of the design. It is the end of the feature. The only reason Microsoft gives publicly is that the change helps streamline the Copilot experience within Excel, and no further technical explanation accompanies it.

AI that lived inside a cell

=COPILOT() began testing in August 2025 for participants in the Microsoft 365 Insider and Frontier programs. You passed a prompt as an argument, optionally along with a cell range, and the model's response came back as the result of the formula. It could also spill across multiple cells as a dynamic array.

The interesting part was that it sat inside Excel's calculation engine. When a referenced cell changed, the AI output recalculated automatically. Classification and summarization could be embedded in the sheet with the same reflexes you use for SUM or VLOOKUP. Sorting free-text survey answers into categories, or drafting descriptions from a column of product names, could live as part of the workbook's logic in a way that no other approach quite matched.

The prerequisites were less convenient. A Copilot license and an internet connection were both required, and the number of calls was capped. The limit is 100 calls per 10 minutes, and going over it leaves #CONNECT in the affected cells. Because copying a working single-cell formula down a column fires a separate request for every row, a table a few hundred rows deep could hit the ceiling easily.

There was also a deeper mismatch: the results are not deterministic. If the model is updated, or if recalculation happens at a different moment, the same formula is not guaranteed to return the same value. Placing that next to functions where opening the file tomorrow must produce yesterday's answer was always an odd pairing. In a shared workbook, results also varied depending on whether the other person held a license, which made distribution awkward.

The side pane is the successor, but not the same thing

Microsoft points users to the Copilot side pane in Excel as the alternative. Summarizing text, classifying data, generating content, and retrieving information from the web can all be handled there, and the company says it covers much of what people did with =COPILOT().

It is, however, a different mechanism. The side pane is a conversational surface, not a formula that lives in the sheet. It does not follow changes in referenced cells, spill into a range, or persist as part of the workbook's logic. Anyone who built a repeatable pipeline out of these formulas will have to rebuild that part.

The recommendations Microsoft gives administrators follow from this. Review internal training material and documentation for references to =COPILOT(), inform affected users about the retirement and direct them to the side pane, and audit any workflows that depend on the function so they can be moved to supported Copilot experiences.

What to do before September 14

If =COPILOT() is already in use in a workbook, those formulas stop working after September 14. To keep the output, freeze it into values before the deadline. Copy the cells and use Paste Values (Ctrl+Shift+V), and the text remains without the formula behind it.

To find the affected cells, searching formulas for COPILOT( is the quickest route. Workbooks scattered across shared folders or SharePoint are the easiest to overlook, so mapping the scope now avoids a scramble once September arrives.

Summary

=COPILOT() was an ambitious attempt to place AI responses inside a spreadsheet's recalculation model, but the general availability plan was withdrawn alongside it and the function ends on September 14, 2026, roughly a year after the preview began. The Copilot side pane offered as its replacement overlaps in capability but does not behave like a formula anchored in the sheet. For existing workbooks, the practical response is to convert results into values before the deadline and re-examine any workflow that leans on the function.