Monthly reporting rarely fails because one formula is difficult. It fails because the same small checks are easy to skip: a changed header, a percentage shown as a decimal, a blank region, or a summary that was not refreshed.
A Copilot skill for Excel gives Copilot a reusable instruction set for that routine. The reliable approach is to require visible QA results in the workbook—not just a chat message saying the report looks fine—and then have a person review those results before sharing the file.
This guide shows how to create a valid custom skill, use it for a monthly report checklist, and keep workbook-specific instructions separate from reusable instructions.
Quick Solution: Create a Valid Skill That Leaves Evidence
A custom Excel skill uses a SKILL.md file with required YAML frontmatter. Put each skill in its own OneDrive folder, and make the folder name match the name in that frontmatter. Then add and enable it through the Copilot in Excel skills experience.
Build the skill around evidence: a QA sheet, issue counts, row or cell references, and a reviewer decision. Do not use a vague instruction such as “clean up this report.”
Step 1: Create the skill folder and SKILL.md file
Create this folder in OneDrive:
monthly-report-checklistInside that folder, create a plain-text file named SKILL.md. The folder name and the frontmatter name must match.
---
name: monthly-report-checklist
description: Prepare a monthly Excel report for review by checking required fields, applying approved display formats, and creating a visible QA review record without changing source values or formulas.
---
# Monthly Excel Report Checklist
Purpose: prepare the current workbook for monthly review without changing source values or formulas.
1. Identify the primary report sheet and the summary sheet. If more than one sheet is a plausible match, ask me to choose.
2. Check whether the primary report contains these headers: Month, Region, Product, Revenue, Margin %, Owner.
3. Create a sheet named QA Review if it does not exist.
4. If QA Review already exists, do not delete or replace its prior contents. Add a new dated review section for the current report period.
5. In the new QA Review section, list:
- missing expected headers
- blank cells in Month, Region, Product, Revenue, and Owner
- Revenue values that are not numeric
- Margin % values outside -100% to 100%
- duplicate rows based on Month, Region, and Product
6. For every issue listed, include the issue type, source sheet, row or cell reference, and value found where available.
7. Apply these formats only to the primary report data area:
- Revenue: currency with two decimals
- Margin %: percentage with one decimal
- Month: the workbook's existing month/date style; do not convert text values automatically
8. Check that the summary sheet clearly identifies its source and period. Do not rebuild summary formulas or PivotTables unless specifically asked.
9. Add Review Notes with counts for each issue type and blank fields for Reviewer decision, Reviewer name, and Review date.
10. Do not delete rows, overwrite source values, change formulas, alter connections, or hide errors.
11. Finish with a short summary of changes made, issues found, and items requiring human review.Expected result: the workbook contains a preserved QA record rather than a disposable chat summary. Existing review history stays intact because each run adds a dated section instead of replacing the QA sheet.
Step 2: Add and enable the custom skill in Excel
- Save the completed skill folder to OneDrive.
- Open Excel and open the Copilot pane.
- Open Skills, then choose Manage skills.
- Choose the option to create or add a custom skill, and select the OneDrive folder containing SKILL.md.
- Review the skill name and description, then enable the skill.
- Use the skill with a saved working copy of your monthly workbook. Return to Manage skills later to disable, edit, or remove it.
The exact labels can vary as Microsoft updates Copilot. Microsoft’s instructions for creating and managing Excel skills are the source of truth for the current creation and management flow.
Step 3: Check availability before designing the process around it
Excel skills require an eligible Copilot setup, OneDrive storage, and a supported Excel environment. Microsoft also notes that skills and rules are currently English-only. If Skills is not available in your Copilot pane, do not substitute an untested workflow; check the Microsoft requirements and use your existing manual checklist until access is confirmed.
Why a Reusable Skill Is Better Than Repeating a Prompt
A monthly report task has two kinds of instructions. Stable instructions across many workbooks—create a QA record, flag blanks, preserve formulas, and request review—belong in a reusable skill.
Instructions that apply to only one workbook belong in workbook rules. For example, the meaning of “Net Revenue,” an approved fiscal calendar, or an allowed exception should not be assumed by every workbook that uses the skill.
| Need | Best place | Example |
|---|---|---|
| Same monthly workflow across files | Reusable skill | Create QA Review and preserve source formulas |
| Definitions unique to one workbook | Workbook rules | “Approved” means status is Signed Off |
| One-off request | Chat prompt | Explain why March revenue fell |
| Specific workbook edit | Reviewable edit request | Format the selected Revenue column as currency |
Microsoft describes rules as workbook guidelines and skills as reusable resources. See its official explanation of Copilot in Excel rules and ExcelJump’s guide to workbook-specific Copilot rules before deciding where a requirement belongs.
Build the Monthly Checklist Before You Automate It
Start with a procedure that a colleague could follow without Copilot. If you cannot define what a blank or duplicate means, a skill cannot make that judgment reliably.
Example report layout
| Month | Region | Product | Revenue | Margin % | Owner |
|---|---|---|---|---|---|
| 2026-01 | East | Service Plan | 12500 | 0.32 | R. Khan |
| 2026-01 | West | Service Plan | 0.29 | M. Lee | |
| 2026-01 | East | Service Plan | 12500 | 0.32 | R. Khan |
| 2026-01 | North | Hardware | 8400 | 1.25 |
For this data, QA Review should show one blank Revenue value, one blank Owner, one duplicate Month/Region/Product combination, and one Margin % outside the stated range. It should not silently “fix” the 125% margin. That value needs a business decision.
Define the boundaries in plain language
- Allowed changes: formatting, QA labels, and review notes.
- Protected items: source values, formulas, source connections, and rows.
- Evidence: issue type, sheet, cell or row reference, value found, and issue count.
- Escalation: values outside business thresholds, missing columns, and refresh failures.
The key point is that formatting and data correction are different jobs. Let the skill standardize formatting and evidence. Send data corrections to a reviewer. If your team needs a separate follow-up record, use an Excel exception log for unresolved report issues.
Run the Skill in a Controlled Monthly Workflow
- Save a working copy first. Use a clear period in the file name, such as Sales Report 2026-01 – Review.xlsx.
- Confirm the input range. Prefer an Excel Table with consistent headers. Blank rows and merged cells make checks harder to interpret.
- Run the reusable skill. State the report period and identify the primary report and summary sheets when the workbook has several candidates.
- Inspect QA Review. Check listed rows against the source sheet. Confirm whether a blank is truly blank or a formula returning an empty string.
- Check the summary separately. If the report uses a PivotTable, follow a defined refresh process and verify the reporting period afterward. A refreshable PivotTable report workflow helps because a refreshed summary can still point at the wrong range.
- Record the reviewer decision. Enter Approved, Approved with exceptions, or Returned for correction, plus a name and date.
Copilot in Excel includes Edit, Plan, and Chat workflows. Use the planning workflow to clarify a multi-step job before applying edits, and use chat for follow-up questions. Refer to Microsoft’s Copilot in Excel getting-started guidance for current mode availability and behavior.
Test the Skill Before You Trust It
Test on a copy containing deliberate issues. Do not begin with the board-ready workbook.
| Test case | What you should verify | Human action |
|---|---|---|
| Header renamed to Sales | QA Review flags missing Revenue | Decide whether Sales is an accepted equivalent |
| Revenue stored as text | Issue is listed; source is not overwritten | Correct the import or convert with approval |
| Formula returns “” | It is identified according to your blank definition | Determine whether the result is expected |
| Repeated key values | Duplicates are listed with row references | Confirm whether they are duplicate records or valid lines |
| QA Review already exists | Prior notes remain and a new dated section is added | Confirm the review history is readable |
Also test formula-related suggestions before accepting them. Use a separate exception list rather than allowing AI to rewrite workbook logic without inspection. Our guide on how to test Copilot-generated Excel formulas provides a practical validation process.
Common Mistakes and Fixes
| Problem | Likely cause | Better approach |
|---|---|---|
| The skill does not appear | Missing frontmatter, incorrect file name, or folder/name mismatch | Use SKILL.md, include YAML frontmatter, and match the folder name to name |
| The skill gives a neat summary but no proof | Instructions ask for analysis, not an output artifact | Require QA Review, row references, counts, and review notes |
| It edits values that should be preserved | Permissions are too broad | State “do not overwrite source values or formulas” explicitly |
| It misses a special workbook rule | Local context was put only in a reusable skill | Add that guidance to workbook rules |
| It reports blanks that are not errors | No business definition of a required field | List required columns and allowed blank conditions |
| The report is refreshed but still wrong | Refresh was treated as proof of correctness | Check source range, period filter, totals, and exception output |
Monthly Review Checklist
- Confirm that Skills is available for your account and Excel environment.
- Keep the approved process in a valid OneDrive skill folder.
- Use the current workbook template and save a working copy.
- Verify that QA Review identifies the report period and source sheet.
- Inspect every issue category and sample the listed cells.
- Refresh and validate summaries using your established process.
- Resolve or document exceptions; do not hide them.
- Record a human reviewer decision before distribution.
FAQ
Can one skill work for every monthly report?
Usually not without adjustment. Keep the shared process in the skill, but store workbook-specific definitions, sheet conventions, and exceptions in workbook rules.
What must a Copilot skill folder contain?
Each custom skill needs its own OneDrive folder containing a SKILL.md file. The file needs YAML frontmatter, including a name and description, and the folder name should match the frontmatter name.
Should the skill correct blanks and duplicates automatically?
Not by default. It should flag them with evidence. A blank or duplicate can be valid in context, and automatic deletion or replacement can damage the report.
Is a QA sheet better than a chat summary?
For recurring reporting, yes. A worksheet output stays with the workbook, can be reviewed by someone else, and shows what was checked.