Excel's =COPILOT function to be retired on September 14, 2026 — What to check right now

About this article
This article was created using an automated generation workflow leveraging generative AI. Based on the Microsoft 365 Insider Blog update from August 14, 2026, it outlines the scheduled discontinuation of the Excel =COPILOT function and provides practical steps you can take right now to review existing workbooks.

Verification Status: 📘 Confirmed via official Microsoft announcement — Actual behavior on and after September 14, 2026, has not yet been verified.

Microsoft has announced that the Excel =COPILOT function will be discontinued starting September 14, 2026. Meanwhile, Copilot in Excel itself is not being removed; Microsoft points users to the Copilot side pane instead. If you have workbooks where you tested the function, it is safe to identify any dependencies now before you run into issues after the retirement date.

• Microsoft 365 Insider Blog — Bring AI to your formulas with the COPILOT function in Excel

Step 1: Check existing workbooks for =COPILOT

Open the target workbook in Excel and search formulas for the following:

=COPILOT(

If found, do not delete them immediately; instead, make a note of the following:

シート名 | セル | 何を生成していたか | 元データ | 代替方法の候補

Check this area

It is not just the number of cells that matters.=COPILOT If the output of is referenced by other formulas, summaries, or reports, those cells may serve as entry points for subsequent processing.

flowchart LR
    A[元データ] --> B[=COPILOT セル]
    B --> C[別の数式]
    B --> D[表・帳票]
    B --> E[手作業の判断]

First locate B, and then check for dependencies in C, D, and E.

What is changing?

The Microsoft update on August 14, 2026, explicitly states that the =COPILOT function in Excel will no longer be available starting September 14, 2026. It also notes that Copilot in Excel will remain accessible via the side pane.

Understand these two points separately:

• Being retired: The =COPILOT function as a cell formula

• Copilot in Excel as a whole: Alternative usage is provided via the side pane

It is important not to extrapolate "the function is being retired" to mean "Copilot is being completely discontinued in Excel."

Try changing a single location

Select just one cell where =COPILOT was found and write a single sentence in natural language describing "what this cell was doing."

Example:

顧客コメント列を読んで、要点を短くまとめていた

Next, check whether that single task can be reproduced using the Copilot side pane. Rather than migrating all workbooks at once, it is safer to observe the differences using a task equivalent to a single cell.

Here, do not assume that "the side pane will yield the exact same results." This is because the operation method, reproducibility, automatic recalculation, and references from other cells have different characteristics.

Formulas and the side pane are not the same thing

Formulas remain in cells and involve recalculation and reference relationships. AI operations via the side pane have a different workflow, even though both are features for "using AI in Excel."

Therefore, during migration, rather than simply copying prompts, check the following:

• Does it need to re-execute automatically?

• Are outputs referenced by other cells?

• Must the exact same result be reproducible every time?

• Is it operationally acceptable for a human to review and then paste the result?

• Should the process be replaced with non-AI alternatives like Power Query, Office Scripts, or standard formulas?

For business use

If your administrative department was using =COPILOT on a trial basis, it is practical to perform the following inventory by September 13 to minimize inquiries after September 14:

1. =COPILOT(Identify workbooks containing

2. Create a list of target cells and their purposes

3. Verify whether subsequent formulas or reports reference them

4. Test on a single item whether the side pane can serve as a substitute

5. Separate processes that would be more stable if replaced with standard functions, Power Query, or Office Scripts instead of AI

6. Flag any procedure manuals or training materials containing =COPILOT for updates

Particularly for routine processes, this also serves as an opportunity to review whether tasks can be handled deterministically using standard Excel features rather than "using an AI function just because it is available."

Re-verifying after September 14, 2026

This article is based on Microsoft's advance notice as of September 13. Actual retirement behavior, existing cell displays, error details, and differences across tenants and channels must be re-verified on actual devices on or after September 14.

Once actual verification is possible, update the content by distinguishing between advance notices and actual behavior.

Official / Primary Sources

• Microsoft 365 Insider Blog — Bring AI to your formulas with the COPILOT function in Excel