Excel's =COPILOT() Dies September 14
The side pane is not a drop-in replacement. A formula recalculates, spills into a range, and lives in the workbook. A chat panel does none of those things.
Founder, Automation Squad ·
The short answer
Microsoft is retiring the =COPILOT() function in Excel after September 14, 2026, under Message Center notice MC1454373. Existing formulas using it stop working on that date. Microsoft directs users to the Copilot side pane and the Dynamic Action Button instead, neither of which is formula-addressable.
Find every =COPILOT() formula you own, and know what replaces it
Four weeks to the deadline. The audit is the slow part — the replacement decision is usually obvious once you can see what the formula was doing.
Search every workbook for the string COPILOT(
In Excel, Find and Select → Find, tick "Look in: Formulas", and search across the workbook rather than the sheet. Do this for shared workbooks too — the ones on SharePoint that six people touch are exactly where an unowned formula hides.
Note what each formula was actually for before deciding anything
Summarising, classifying, generating, or looking up. The replacement differs per case, and the decision is quick once the purpose is written down.
Understand precisely what you lose
A worksheet function recalculates when its inputs change, spills results into a range, and is visible as part of the workbook's logic. The side pane does none of that. If your process depended on any of those three behaviours, you need a script, not a panel.
For anything genuinely per-row and repeating, look at Python in Excel or an Office Script
These keep the work inside the file and inside a refreshable process, which is the property you are actually trying to preserve. A one-off side-pane answer pasted into a column is not a process.
Warn whoever else opens the workbook
On September 15 the formula stops returning a value. If the workbook feeds a report someone else reads, they will see the breakage before you do and will not know why.
Put the date in the calendar now, for a week before
September 7 gives you a working week of margin. Deadlines that land mid-month are the ones people intend to handle and then don't.
| What your formula was doing | Where it goes now |
|---|---|
| Summarising a text column | Copilot side pane, or Python in Excel |
| Classifying / tagging rows | Python in Excel, or an Office Script calling an API |
| Generating short content per row | Office Script + API call, batched |
| Looking something up on the web | Copilot side pane (not per-cell) |
| Numeric calculation | Never use it for this — Microsoft advised against it |
| Pulling data already in the workbook | Ordinary formulas — Microsoft advised against COPILOT() here |
| Anything under legal or compliance requirements | Microsoft advised against COPILOT() for this too |
Take it with you
EXCEL =COPILOT() RETIREMENT — deadline Sept 14, 2026
Microsoft 365 Message Center: MC1454373
Source: https://automationsquad.com/news/excel-copilot-function-retiring/
WHAT HAPPENS
The =COPILOT() worksheet function stops working after Sept 14, 2026.
Microsoft: "We have decided not to move forward with this feature."
You are directed to the Copilot side pane and the Dynamic Action Button.
WHAT YOU ACTUALLY LOSE (the side pane does NOT do these)
- recalculates when referenced cells change
- spills results into a range
- lives visibly inside the workbook's logic
THE AUDIT
[ ] In each workbook: Find and Select > Find
search "COPILOT(" with Look in: FORMULAS
scope to WORKBOOK, not sheet
[ ] Include shared/SharePoint workbooks — that's where unowned
formulas hide
[ ] For each hit, write down what it was FOR:
summarise / classify / generate / web lookup
WHERE EACH ONE GOES
Summarising text column ..... side pane, or Python in Excel
Classifying / tagging ....... Python in Excel, or Office Script + API
Generating content per row .. Office Script + API, batched
Web lookup .................. side pane (not per-cell)
Numeric calculation ......... never was appropriate
Data already in the workbook ordinary formulas
Legal/compliance content .... was never advised
[ ] Tell anyone else who opens the workbook — they'll hit the
breakage before you do
[ ] Calendar reminder for Sept 7 (a week of margin)Microsoft confirmed on August 17, 2026 that the =COPILOT() function in Excel will be retired. Message Center notice MC1454373 states the function will no longer be available after September 14, 2026 — around a year after it entered preview for Frontier and Insider Microsoft 365 Copilot licensees.
The facts: the function let you write natural language into a cell and receive an AI-generated result in the worksheet, and worked best for summarisation, classification, content generation and web lookup. Microsoft explicitly did not recommend it for numerical calculation, for retrieving information already present in the workbook, or for content subject to legal and compliance requirements. Microsoft's reason for retiring it is that it has "decided not to move forward with this feature." Users are directed to the Copilot side pane and the Dynamic Action Button. Google Sheets retains its equivalent AI function.
Automation Squad's take: the replacement advice is where this gets frustrating, because a side pane is not what a worksheet function is. Three properties made =COPILOT() interesting and none survive the move — it recalculated when its inputs changed, it spilled into a range, and it sat visibly inside the workbook so the next person could see what was happening. A chat panel produces an answer you paste somewhere. That is a different tool for a different job, and describing it as the path forward papers over the gap. The honest read is that Microsoft tried putting a model inside the formula grammar, found it did not work out, and is reverting to the assistant pattern. Anyone who built a genuine process on it has four weeks and no drop-in option.
Run this now: open each workbook that might use it and search for "COPILOT(" with Find and Select, making sure to look in Formulas and to scope the search to the workbook rather than the active sheet. Shared workbooks matter most here, because a formula nobody owns is the one that breaks silently in September. For every hit, write down what it was doing before deciding what replaces it — summarising and looking up are fine in the side pane, but anything that genuinely needs to repeat per row and refresh needs Python in Excel or an Office Script instead.
Questions people are asking
- When exactly does the Excel COPILOT function stop working?
- After September 14, 2026, per Microsoft 365 Message Center notice MC1454373. Formulas using =COPILOT() stop returning values from that point.
- Why is Microsoft retiring it?
- Microsoft's stated reason is simply that it has decided not to move forward with the feature. It had been in preview for roughly a year, available to Frontier and Insider Microsoft 365 Copilot licensees.
- Is the Copilot side pane a replacement?
- Not a direct one. A worksheet function recalculates when its inputs change, spills results into a range, and forms part of the workbook's visible logic. The side pane and the Dynamic Action Button do none of those, which matters if your process depended on refresh rather than on a one-off answer.
- What should I use instead for per-row AI work?
- For work that genuinely needs to repeat per row and refresh, Python in Excel or an Office Script calling an API keeps the process inside the file. For one-off summarisation or lookup, the side pane is fine.
Sources
Further reading
- The Register — Excel's Copilot function is headed for the Recycle Bin — The clearest account of what the function did and what the side pane cannot replace.
Last checked August 17, 2026 against the primary sources above, by Automation Squad Research. Spot an error? [email protected].