Copilot in Excel for beginners: compare budget to actuals

Budget: 120,000. Actual: 132,000. The result is 12,000 over budget. Three rows have been checked, and one column was added. You can review that result. A workbook full of unexplained AI edits is much harder to trust.

Our earlier article Before Copilot changes your budget: ask for a change plan explains the plan-first idea. This guide applies it to a copy of a real workbook and ends with a short review log.

Who this guide is for

This guide is for people who already use Excel for a budget, forecast, or resource plan and want to give Copilot one defined job. The main example follows a consultant comparing budgeted and invoiced revenue by project for one month. The same steps work for supplier costs or planned versus actual resource use.

You need to understand what the Budget and Actual columns mean. You do not need to write the formula yourself.

What you will learn in 10–20 minutes

After this guide, you can:

• open a copy of a workbook,
• ask Copilot for a plan without editing,
• check the period, ranges, and sign convention,
• approve one Variance column,
• verify three rows and save a review log.

Where to find Copilot in Excel

Go to https://excel.cloud.microsoft/, sign in, and open a copy of your workbook. Select the Copilot icon in the lower-right corner of Excel.

Copilot normally opens in Allow editing, where it can change the workbook directly. Switch to Plan before sending the first prompt. The third mode is Chat only, which keeps responses in the chat instead of changing the file.

If the Copilot button is missing, access can depend on your license, app version, network or privacy settings, and organization configuration. Copilot editing also requires Calculation Options to be set to Automatic. Microsoft lists Swedish among the supported prompt languages, although results can vary across languages and workbooks.

Source: Microsoft Support: Get started with Copilot in Excel.

Source: Microsoft Support: Frequently asked questions about Copilot in Excel.

Before you start

Use a copy and choose one period. Confirm which sheets or columns contain Budget and Actual. Write down:

• the currency or other unit,
• whether costs appear as positive or negative numbers,
• the period covered by the figures,
• known assumptions, such as tax treatment or the invoice cut-off date.

Choose the sign convention before Copilot calculates anything. This guide uses Actual - Budget. A Budget of 10,000 and Actual of 12,000 therefore produces a positive variance of 2,000. For a cost, that means over budget. For revenue, the same positive number may mean above target. The formula is unchanged, but the business meaning is yours.

Step 1: request a plan without edits

Open Plan and paste this prompt:

I want to compare Budget with Actual for [period] in this workbook.

Work in Plan mode. Do not edit any cells yet.

1. Identify the sheets, columns, and ranges that contain Budget and Actual.
2. Briefly explain the existing formulas that affect the comparison.
3. Propose one column where Variance is calculated as Actual minus Budget.
4. List the questions I need to answer about period, currency, signs, and assumptions.
5. Describe the exact single change you want to make and the range it will affect.

Finish with a verification checklist. Wait for my approval before editing the workbook.

Plan mode makes the proposal visible. It does not guarantee that Copilot selected the right sheet, formula, or assumption.

Step 2: check the plan

Read the plan before changing modes. Check five things:

1. Is Copilot pointing to the correct sheet and period?
2. Are Budget and Actual coming from the right cells?
3. Does it use Actual - Budget, and does that sign match how your team reads variance?
4. Are the currency and units consistent?
5. Are there blank cells or zero values that need special handling?

You can select an existing formula cell and ask Copilot to explain it. Microsoft documents that Copilot can create formula columns and explain how formulas work. Understand the calculation before Copilot applies it to the rest of the column.

Source: Microsoft Support: Get data insights with Copilot in Excel.

Step 3: approve one change

Once the plan is correct, switch to Allow editing and send a new, narrow instruction. Plan mode produces the plan; editing mode applies the change.

Apply only the approved change in this workbook copy:

Add a column named Variance and calculate Actual minus Budget for each relevant row.

Do not change any other values, formulas, formatting, sheets, or summaries. When finished, report the exact range changed and explain the formula in one sentence.

Compare the range Copilot reports with the workbook. If it proposes extra changes, stop and narrow the instruction again.

Step 4: verify three rows

Choose three rows that test different parts of the result:

• one ordinary row,
• the largest variance,
• one edge case, such as Budget = 0 or a blank Actual value.

Calculate the ordinary row yourself. For the other two, compare the source cells, formula, sign, and result. Check that the total still reconciles.

Then ask Copilot to rank the three largest variances and show the rows and source cells behind each calculation. Do not ask it to invent a business cause. An unexpected supplier cost or late invoice needs evidence from the workbook or the person responsible for the figure.

Microsoft explicitly tells users to review and verify AI-generated formulas and insights. Treat the variance list as questions for the next budget review, not as an automatic financial decision.

Step 5: save a review log

Save a short note in the project folder, a comment area, or a separate document:

Budget review: [period]
Workbook: [copy name]
Changed range: [cell range]
Formula: Variance = Actual - Budget
Rows checked: [row 1], [row 2], [row 3]
Assumptions confirmed: [list]
Open question: [question and owner]

That note makes next month's review easier. If the file is stored in OneDrive or SharePoint, you can also use Version History to compare or restore an earlier version.

Source: Microsoft Support: View previous versions of Office files.

Common mistakes

• Asking Copilot to "fix the budget" without naming the period, sheets, or columns.
• Approving the formula before agreeing on what a positive number means.
• Mixing currency, hours, people, and percentages in one comparison.
• Treating a large variance as an explanation. It is a row to investigate.

Next step

Repeat the review next period only after the first version has been checked and documented. If the same review returns every month and the team needs the same approval trail each time, Hammer Automation can help map a repeatable version with clear data sources, permissions, and review points.