Review this year's tax returns against last year's with a saved prompt: have AI compare each return line by line with the prior year, flag every big change and show the numbers behind it, then check its flags yourself: AI agent prompt
In a TaxOps podcast write-up published Nov 3, 2026, Betty Mak, U.S. tax director at The Jim Pattison Group, described building her first AI agent in Microsoft 365 Copilot during compliance season to review a high volume of state returns by comparing each one with the prior year's return, her usual review baseline. It made mistakes: it once said her apportionment numbers matched the prior year, which could not have been true, and it capped how many files it would take at once. She said she would not use it to replace a person. Her team later added Claude for larger data sets in Excel, and she plans to store reviewed standard prompts in a shared prompt library (compare against prior year, check apportionment, flag anything unusual) so staff can repeat the process. Her rule is to treat AI like a junior whose work you check.
The prompt
1. Use an AI tool your firm has approved for client data (an enterprise Copilot, Claude or ChatGPT plan). Remove or mask ID numbers you don't need for the check. 2. Put this year's draft return and last year's filed return for the same entity side by side, as PDFs or an Excel export. 3. Ask: "Compare these two returns line by line. Make a table with the line or form reference, last year's amount, this year's amount, the change in dollars and percent. Flag every change over 10% or $[amount], any line that is identical when it probably shouldn't be (for example apportionment factors), and any line that appears in one year but not the other. Quote the figure you read from each document so I can check it." 4. Check every flag against the source documents yourself, especially any 'no change' result; the AI can misread. 5. Write a short note on each real change, or fix the return. 6. Save the prompt that worked in a shared prompt library or your workpapers so it's used the same way on every return next season.
Fill in the blanks, then copy
This prompt has 1 [bracket] to fill in. Type your details below and the prompt updates as you go. Your answers stay in this browser and are reused on other prompts with the same blanks. Nothing is sent to us.
Example values are fictional, just to show how a filled-in prompt reads. Replace them with your real details.How to use it
- Copy the prompt above.
- Replace every [bracket] with your own details (use the fill-in-the-blanks box above, which remembers your answers for the next prompt).
- Paste it into Microsoft 365 Copilot, Claude or ChatGPT (enterprise plan), Excel and review the answer before you use it.
Works with: Microsoft 365 Copilot, Claude or ChatGPT (enterprise plan), Excel
Real-world example: taxops.com/ai-in-the-tax-department/
Featured in: AI prompts for Google Sheets and Excel work
Before you use it: what to check
Already built into this prompt
- Use an AI tool your firm has approved for client data (an enterprise Copilot, Claude or ChatGPT plan).
- Remove or mask ID numbers you don't need for the check.
- Check every flag against the source documents yourself, especially any 'no change' result; the AI can misread.
Check yourself
- Check every figure, price and total against your own records before anything is sent, posted or booked. A person approves refunds, discounts, payments and price changes.
- Anything legal, tax or compliance-related is a first draft for a qualified person to check. It is not professional advice, and clause references and deadlines must be checked against the source.
- Remove names, contact details, account numbers and other personal data the task doesn't need before you paste, and check your AI tool's data and training settings.
- Check names, dates, numbers and any claim against your own source material before you use the answer. AI can misread or invent details.
Using an AI agent? Download this prompt as a SKILL.md agent skill with these checks built in, or get the .zip for Claude.ai. How to install skills.
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