Make a UK tax research agent from a folder of HMRC manuals with Claude Code

Posted

Aug 21, 2025 by Martin Alderson

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Last checked

Oct 16, 2026

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Method:

How we verify

Evidence: Screenshots or logsThe source shows screenshots, a transcript or the agent's output.

Outcome

Using scraped HMRC manuals and legislation plus a CLAUDE.md that launches parallel subagents, Claude Code answered an ATT exam question in about 5 minutes, earning roughly 2.5 of 3 marks by the author's grading.

Agent

Claude Code

The source didn't share its exact prompt, so we wrote this from what it describes.

Here's a task I'd like your help with. Read it all the way through before you start.

Goal: Answer this UK tax question using the tax laws and HMRC manuals in this folder.

Check with me first: What's the question, and do I want a short answer or a full working?

What I'll give you:
- The question
- A folder with the UK tax legislation and HMRC manuals
- Instructions for how you should work (for example a CLAUDE.md file)

Rules:
- Search the documents in the folder and base the answer on them.
- Split the research across parallel helpers, for example corporate, personal tax, current rates and anti-avoidance.
- If something is missing or unclear, ask me instead of guessing.
- Cite the sections you rely on. This is research, not professional advice.

Output: A structured answer with calculations and references to the sources.

You'll know it worked when: the answer is backed by specific sections I can check.

Here's a task I'd like your help with. Read it all the way through before you start.

Goal: Answer a UK tax question using only the legislation and HMRC manuals in this folder, with citations a professional could check.

Quick check first: tell me if anything below is missing or unclear.

Inputs (fill in or confirm):
- The question, with the facts (dates, amounts, residency)
- The folder of legislation and HMRC manuals
- Short answer or full working
- Tax year(s) involved

Rules:
- Search the folder first; cite the exact Act section or manual reference (e.g. a BIM or CG paragraph) for every step.
- Separate what the law says from HMRC's interpretation in the manuals.
- State assumptions about missing facts and how the answer changes if they're wrong.
- Don't rely on memory for rates or thresholds; take them from the folder for the right tax year.
- Flag areas where professional advice is needed.

If you get stuck: If the folder doesn't cover the point, say so plainly instead of filling the gap from general knowledge. If a login, CAPTCHA or two-step code appears, stop and ask me to handle it; never guess or store passwords.

Verify before you finish: Re-open each cited paragraph and confirm it says what you quote.

Output: Answer first (2–3 sentences), then the working with citations, then assumptions and open questions.

Done when: every conclusion traces to a cited paragraph in the folder.

Source

https://martinalderson.com/posts/building-a-tax-agent-with-claude-code/