Rules are automatic instructions that Claude Code follows in every single conversation, without you having to repeat them. Think of them like the written policies you give a new employee on their first day -- the things that apply to every task, every time, regardless of what job they're working on. Rules handle the consistent, non-negotiable standards so you never have to say "always write in UK English" or "never delete a file without asking" more than once.
Where your CLAUDE.md file sets the big picture -- who you are, what your business does, what projects are active -- rules handle the specific, enforceable details. One rule file per concern, each loaded automatically when Claude starts a session.
Where rules live
Rules are stored as ordinary text files inside a folder called .claude/rules/ in your workspace. The dot at the start of .claude means it's a hidden folder -- on macOS, you can see it by pressing Cmd+Shift+. in Finder. Every file ending in .md (a plain text format called Markdown) inside that folder is loaded automatically at session start. You don't run any commands. You don't tell Claude to "load the rules." It happens in the background every time.
Each file handles one concern. That separation is deliberate -- it makes rules easier to update, easier to debug, and easier to share across workspaces without dragging along unrelated instructions.
Why rules matter for business use
Without rules, Claude's behaviour is inconsistent across sessions. It might write in US English one day and UK English the next. It might delete a file when you only wanted to rename it. It might send client documents without the company header. Rules eliminate that variability. They create a baseline of professional behaviour that holds whether you're asking Claude to draft an email, process a spreadsheet, or organise a folder of invoices.
Think of the payoff this way: the ten minutes you spend writing a rule pays back every time Claude gets it right without being told.
What a rule file looks like
A rule file is plain text with a descriptive filename and simple headings. You don't need to know any programming to write one -- just type instructions the way you'd explain them to a person.
# Communication Standards
## Language
- Write in UK English (organise not organize, colour not color)
- Professional but conversational tone
- No jargon unless the client uses it themselves
## What to avoid
- Never start a sentence with "Certainly!" or "Great question!"
- Don't use exclamation marks in client-facing documents
- Avoid passive voice in headingsFour types of rules every business workspace should have
1. Communication standards
These define the voice and language standards Claude should maintain across all written output. Useful instructions include: which variant of English to use, tone (formal vs conversational), prohibited phrases or filler words, and guidance on how to handle technical terms when writing for non-technical audiences.
2. Blocked actions
These tell Claude what it must always ask before doing. Common examples: never permanently delete a file, never send anything externally without approval, never overwrite a file that came from a client. This is your safety net -- the things where the cost of getting it wrong once outweighs the time saved by acting automatically.
Example blocked-actions rule
A rule that says "Never delete any file without showing me what will be deleted and waiting for confirmation" takes 30 seconds to write and will never be forgotten -- unlike a verbal instruction given once in a conversation.
3. Content and brand standards
These ensure every document, email, or report Claude produces matches your brand. Specify: which template to use for client documents, whether to include a company header, what the standard disclaimer text is, how to format dates (UK format: DD/MM/YYYY), and whether to use your logo file path for documents that support images.
4. Autonomy levels
These tell Claude when to act without asking and when to pause for your approval. The principle: low-risk, reversible actions (fix a typo, reformat a table) can happen automatically. High-stakes, hard-to-undo actions (change a client-facing document, send an email, modify financial figures) should always require your sign-off. A well-written autonomy rule gives Claude a clear decision framework it can apply to any situation, not just the ones you anticipated.
How to create your first rule
- Open your workspace in VS Code or a text editor
- Navigate to the
.claude/rules/folder (create it if it doesn't exist) - Create a new file with a descriptive name, e.g.
communication.md - Write your instructions in plain English under clear headings
- Save the file -- Claude will load it automatically in the next session
Start with one rule covering the thing that currently requires the most repetition. If you find yourself correcting Claude's tone every session, write a communication rule. If you're always reminding it not to overwrite files, write a blocked-actions rule. Build from there.
How rules and CLAUDE.md work together
Your CLAUDE.md file is the strategy document. It covers who you are, what your business does, what projects are active, and how the workspace is organised. Rules are the policy layer underneath. They handle the specific, repeatable standards that need to be enforced consistently regardless of what task is in progress.
A useful mental model: CLAUDE.md is the employee handbook introduction. Rules are the actual policies in the appendix -- the ones that spell out precisely what to do and what not to do in specific situations. Both matter. Neither replaces the other.
When a rule conflicts with something in CLAUDE.md, Claude should flag the conflict rather than guess. That's by design -- conflicts usually mean one document was updated without updating the other, and you want to know about it.
Common rules every business workspace should have
| Rule file | What it covers | Why it matters |
|---|---|---|
communication.md | Tone, language variant, prohibited phrases | Consistent voice across all written output |
blocked-actions.md | Commands and actions requiring confirmation | Prevents irreversible mistakes |
content-standards.md | Templates, headers, branding requirements | Professional, on-brand documents every time |
autonomy-levels.md | When to act vs when to ask | Balances speed with appropriate oversight |
credentials.md | Never accept passwords or tokens in chat | Basic security hygiene |
file-organisation.md | Where files go, naming conventions | Consistent workspace structure |
You don't need all of these on day one. Pick the one that addresses the most friction in your current workflow and build the set gradually as patterns emerge.