Why deleting by hand is a trap
A bookkeeper in my community told me she deletes every client's name and number by hand before she uses AI. Every single time. It takes ages. And here's the scary bit — one busy day, she'll miss one. That one slip is a client's private info, gone to a computer she doesn't control.
There's a better way. You get the computer to do the hiding for you — the same way, every time. You set it up once. Then it never gets tired, never gets bored, and never forgets.
😮💨 Doing it by hand
- Slow — you redo it every time
- Boring, so you start rushing
- Easy to miss one name or number
- One miss = real data leaked
✨ A little helper does it
- Done in a few seconds
- Exactly the same every time
- Never gets tired or distracted
- You literally can't forget
The one rule that keeps it safe
This is the most important page in the whole kit. Read it twice. It's also the answer to "can I just do this in Cowork?" — yes, as long as you follow this rule.
The rule
Do NOT paste your client's real info into the chat and ask AI to hide it. The second you hit enter, the AI has already seen it. Too late.
Instead: get AI to build you a little helper (a tiny script). The helper lives on your computer. The helper hides the private stuff. Only the safe, hidden version ever goes to AI.
Build the helper once
AI writes the little script for you. The script is just instructions — it has none of your client data inside it. Totally safe to make.
Run the helper on your file
This happens on your computer. The helper reads the file and hides the private bits. Your real data never goes anywhere.
Now use AI
You only ever hand AI the safe, hidden version. It can help you all day and never see a real name.
The mistake to avoid
Never paste a real client file into the chat and type "redact this". The AI sees it the moment you send it. Always: build the helper, then run the helper.
What counts as client info
Before you hide things, you need to know what to hide. In Australia, these are the bits that matter most. Your helper should look for all of them.
Names
People and business names. Swap each for CLIENT_1, CLIENT_2, and so on.
Tax File Number
The TFN — 9 digits. Becomes TFN_1. This one's serious; never let it slip.
ABN
Australian Business Number — 11 digits. Becomes ABN_1.
BSB & account number
Bank details. Becomes BSB_1 and ACCOUNT_1.
Emails & phones
Email addresses and phone numbers. Become EMAIL_1 and PHONE_1.
Addresses & DOB
Home or postal addresses and dates of birth. Become ADDRESS_1 and DOB_1.
A simple way to think about it
If a stranger could use it to find, contact, or pretend to be your client — hide it. When in doubt, hide it.
Do it in Cowork (no terminal)
This is the easy way. Nothing scary, no black screen with code on it. You use Claude Cowork — the desktop app. If you've never touched the terminal, start here.
Make a folder
On your computer, make a folder called something like "Client work — safe". Pop the file you want to use (your spreadsheet, say) inside it.
Open Cowork and connect the folder
Open the Claude desktop app, go to Cowork, and connect that folder so Claude can see it.
Ask it to build the helper
Copy the prompt below and send it. Notice — you're asking it to build the tool, not to read your data.
Run the helper
Say: "now run it on my-file.csv". It makes a safe copy with all the private bits hidden.
Work on the safe copy
Now do your real job — "find the mistakes in this", "summarise this", whatever you need. AI only ever sees the safe version.
Copy-paste this into Cowork
That's it. It builds your helper. From now on you just say "redact this file" and it does the hiding for you.
Why this is safe
The helper does the hiding on your own computer. You only ever ask Cowork to work on the safe copy. Extra careful? Run the helper yourself and only ever open the safe copy with AI.
Do it in Claude Code
Prefer Claude Code (the terminal one)? Same idea, here's the short version. If that last sentence meant nothing to you — skip this and use Cowork above. Both end up in the same place.
Open Claude Code in your folder
Point it at the folder with your file in it.
Ask it to build the script
Paste the prompt below. It writes a little file called redact.py.
Run it
Say "run redact.py on clients.csv". The script does the hiding right there on your machine.
Use AI on the safe file
It hands you a clean, hidden copy. Use that for everything else.
Copy-paste this into Claude Code
Same safety, same rule
The script runs on your computer. Your real data never goes to the cloud. AI only ever reads the safe copy it made.
Hide → use AI → swap back
Here's the whole thing in plain words, with a real example. Three little steps.
What's actually happening
The payoff
Same insights. Same time saved. But none of your client's private stuff ever left your computer. That's the whole game.
Check it worked & reuse it
Don't just trust it — check it. This takes 30 seconds and you should do it every time until you're sure your helper is solid.
The 30-second leak check
Open the safe copy. Press Ctrl+F (or Cmd+F on a Mac) and search for one real client name, then one real number. If it finds nothing — you're good. If it finds something, tell AI "you missed this one, add it to the helper" and run it again.
Make it a one-click thing
Once it works, say: "save this as a skill called redact". Next time you just say "redact this file" and it's done. You can also point it at a whole folder and have it clean every file at once.
You just removed the scariest part of using AI for client work
No more hand-deleting. No more "what if I missed one". A two-minute setup, and you can finally use AI on real work without the worry. That's a proper unlock.
Ready to go deeper?
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