Microsoft lists September 14, 2026 as the date the Excel =COPILOT() worksheet function becomes unavailable. The change affects the preview function that placed AI prompts inside cells. Copilot in Excel continues to support AI-assisted work through its separate interface.
Checked September 14, 2026. This is the effective date of an already announced change. We verified Microsoft’s documentation; we did not test the retirement on a live customer workbook.
What is ending?
The official COPILOT function notice identifies the function offered through the Frontier and Microsoft 365 Insider programs. Its prompts could use supplied cell ranges for tasks such as text generation and classification. A workbook using ordinary formulas such as SUMIFS is a different case.
The notice does not establish one universal post-retirement error message for every existing workbook. Do not diagnose a file solely from a screenshot of an error: inspect the formula and confirm which feature it uses.
What remains available?
Microsoft’s current Copilot in Excel guide describes help with formulas, tables, charts, and workbook editing. It distinguishes chat, plan, and edit modes. Availability depends on the platform, qualifying subscription, and organization settings.
In that guide, chat mode keeps answers in the conversation, plan mode prepares an approach, and edit mode can change the workbook. Select the mode appropriate to your task and inspect any changes before relying on them. A subscription name alone does not prove that every device supports every mode.
A workbook review checklist
Our suggested workflow: work on a copy and keep the original file intact. These are editorial review steps, not a claim that Microsoft automatically migrates old formulas.
- Find affected formulas. In desktop Excel, open Find and its Options, set Within: Workbook and Look in: Formulas, and search for
COPILOT(. Leave Match entire cell contents and Match case unchecked, clear any format filter, and use Find All. Microsoft documents these settings in its Find guide. Web and mobile controls may differ. Examine each match, including formulas wrapped in another function. Record the sheet, cell, prompt, and referenced range. - Preserve useful results carefully. If an old result is still visible, review it and retain a dated snapshot in a separate sheet or file. Values preserve an output; they do not preserve a working AI formula or prove that the output is accurate. If a cell already shows an error, pasting its value will not recover an earlier answer. Look for a previously saved copy or reviewed export instead.
- Separate language work from arithmetic. Classifying a written comment needs different checks from adding invoice amounts. Define the expected result before choosing a replacement.
- Test a small sample. Include an ordinary row, a blank, and an ambiguous entry. Compare outputs with your own answer key before applying the approach to a full column.
- Check dependent work. Review totals, charts, filters, and reports that read the affected cells. A successful replacement in one cell does not confirm the whole workbook.
Example: replace a calculation with a checkable formula
Suppose B2:B7 contains regions, C2:C7 contains payment status, and D2:D7 contains amounts. With numeric amounts and consistent region/status text, enter this English Excel formula in G2 to total paid orders for the region in F2. Some local settings use semicolons instead of commas:
=SUMIFS($D$2:$D$7,$B$2:$B$7,F2,$C$2:$C$7,"Paid")If the matching paid amounts are 120, 0, and 20, the answer should be 140. A new row 8 is outside those fixed ranges, so it will not be included unless the ranges or table references are adjusted. This example illustrates verification; it is not a universal conversion for old AI prompts.
For a full worked example, use our guide to writing and testing Excel formulas with AI. For text and table preparation, see cleaning spreadsheet data with AI and choosing an AI data-analysis workflow.
Before sharing a revised workbook
Keep a short change log: affected cells, replacement method, test cases, and the person who reviewed the results. Send the workbook only after checking its downstream outputs. If you cannot determine how a business-critical file depends on the old function, ask its owner to review the copy before replacing the original.