Paste this prompt into any AI system - Claude, ChatGPT, Gemini - and it will treat every tax question like a disciplined tax professional: cite the IRC section, flag uncertainty, never fabricate thresholds, and tell you when it does not know.
This is a system prompt - a set of instructions you give the AI before your conversation. In Claude, paste it into the system prompt field or start your conversation with it. In ChatGPT, use Custom Instructions. In any AI, simply paste it at the beginning of your chat.
This prompt is free to use, share, and modify. Attribution appreciated but not required. Learn about the project.
In Claude.ai, create a Project and paste this into the Project Instructions. Every conversation in that project will follow these rules automatically. Or paste it at the start of any new conversation as your first message.
Go to Settings → Personalization → Custom Instructions. Paste the prompt into the "How would you like ChatGPT to respond?" field. It will apply to all future conversations.
Copy the prompt, paste it as your first message in any AI chat, then ask your tax question on the next line. The AI will adopt the protocol for that conversation. Works with Gemini, Perplexity, Copilot, and any LLM that accepts instructions.
Here is the same tax question answered without the prompt and with it.
Q: Is my home office deductible? A: Yes, if you use part of your home exclusively and regularly for business, you can deduct home office expenses. The deduction can be calculated using the simplified method ($5 per square foot, up to 300 sq ft) or the actual expense method.
Q: Is my home office deductible? A: Depends on your employment status and how the space is used. VERIFIED LAW (IRC §280A): A home office deduction is available if a portion of the home is used regularly and exclusively as the principal place of business or for meeting clients. Two methods: simplified ($5/sq ft, max 300 sq ft per Rev. Proc. 2013-13) or actual expenses (proportional to business-use percentage). KEY DISTINCTION - VERIFY FOR YOUR SITUATION: Employees (W-2): Home office deduction is NOT available for 2018-2025 under TCJA (IRC §67(g) eliminated miscellaneous itemized deductions). Confirm whether OBBBA extended any employee deduction - I cannot confirm this without current guidance. Self-employed (Schedule C): Deduction available subject to §280A limitations. Deduction cannot exceed gross income from the business activity. MISSING FACTS I NEED: Are you an employee (W-2) or self-employed? What is the dedicated square footage and total home square footage? CERTAINTY: The self-employed analysis is VERIFIED LAW. The employee analysis for post-2025 is UNCERTAIN - verify with a CPA given recent legislative activity.
The second answer is longer but it is actually useful. It tells you what it does not know, what it needs from you, and where to verify. The first answer feels complete but is missing the most important fact: W-2 employees generally cannot take this deduction at all under current law.
Add COACHING MODE ON to any tax question and the AI will include a practitioner-level analysis of what made the question complex, what a CPA would look for that a non-expert might miss, and what you should ask your tax advisor.
This turns the AI into a study partner - not just an answer machine. Over time, you learn which questions require a professional, which follow-up questions to ask, and how to think about tax problems the way a practitioner does.
COACHING NOTE: This question has three layers most people miss. (1) The employment status split is the most common error - people assume the deduction works the same for employees and self-employed. It does not. (2) The "exclusive use" requirement is stricter than it sounds. A desk in a room that is also used as a guest bedroom does not qualify. The IRS scrutinizes this heavily on audit. (3) The income limitation (§280A(c)(5)) prevents home office deductions from creating or increasing a net loss from the business. This surprises people in early-stage businesses with pre-revenue losses. COMPLEXITY RATING: MODERATE QUESTIONS FOR YOUR CPA: 1. Does my home office use qualify under the exclusive use test given how I use the space on non-work days? 2. Is my gross income from this activity sufficient to absorb the full deduction? 3. Given my W-2 income, does electing S-corp status change my home office deduction availability?
The prompt is free - copy it, share it, build on it. The only thing we ask: if you share it, link back to this page so others can find the validated tax reference library it draws from.
Part of the tk.cpa AI Lab project - building guardrails for AI in tax. If you are a licensed CPA or EA who wants to validate content, join the validator network.