Most AI mistakes are not dramatic. Nobody gets hacked. Someone simply pastes something into a chat window that should never have left the building, and only realises later. The good news is that this is completely avoidable with one rule and a short list you can hold in your head.

This is general guidance, not legal advice. If you handle particularly sensitive data or you are unsure about your obligations, check with a professional who knows your situation.

The one rule that covers almost everything

Before the list, here is the rule that makes the list mostly unnecessary:

If you would not put it in an email to a stranger, do not paste it into an AI tool.

That single test catches the vast majority of cases. An AI chat is not a private notebook. It is a message you are sending to an outside company’s computer. Treat it with the same care you would treat any message leaving your business, and you will rarely go wrong.

Now, the specifics.

What to keep out

Passwords and logins. Never paste a password, a PIN, a security question answer or an API key into a chat. There is no good reason to, and every reason not to. If you need help writing something that involves a login, describe the situation and leave the actual credential out.

Card and bank details. Full card numbers, sort codes, account numbers. AI tools are not payment systems and have no business holding this. If you are drafting an invoice or a payment chase, write “[bank details here]” as a placeholder and fill it in yourself afterwards.

Other people’s personal data. This is the big one for most businesses. Customer names tied to addresses, phone numbers, email addresses, dates of birth, health details, anything that identifies a real person. This is exactly the data that data-protection rules are built to protect, and pasting a spreadsheet of it into a random tool is where owners get into genuine trouble. You almost never need to.

Confidential and legal documents. Signed contracts, NDAs, anything marked confidential, anything covered by a confidentiality clause with a client. If a document says “do not share this”, an AI chat counts as sharing.

Staff and HR information. Salaries, disciplinary notes, references, anything from a personnel file. This is personal data with extra sensitivity attached. Keep it out.

Anything about a live legal or safety matter. An ongoing dispute, an insurance claim, an accident report. Get proper advice on these rather than talking them through with a tool that might remember the details.

Trade secrets and your crown jewels. Your secret recipe, your pricing model if it is genuinely confidential, source code you would not want a competitor to have. Judge these case by case, but err on the side of caution.

The trick: you rarely need the real details

Here is what makes all of this easy. The AI almost never needs the sensitive bits to do the job you actually want.

Look at the difference:

  • Instead of pasting a customer’s full record: “Draft a friendly reply to a customer who is unhappy that their delivery is three days late and wants to know when it will arrive.”
  • Instead of pasting a signed contract: “Explain in plain English what a limitation of liability clause usually means, so I know what to look for in a contract.”
  • Instead of pasting a staff member’s file: “Help me write a fair, professional message asking a team member to improve their timekeeping.”

In each case the AI does exactly the work you needed, and none of the sensitive data ever left your desk. This habit is called anonymising, and it is the single most useful safety skill you can build. Strip out the real names, numbers and identifiers, describe the situation, and let the tool work on the shape of the problem rather than the private detail.

What is usually fine to paste

To keep this from feeling like a wall of “no”, here is the other side. It is generally fine to paste:

  • Text you wrote yourself and would happily share, to be tidied or shortened.
  • Public information: your own website copy, a published article, a public price list.
  • Made-up or anonymised examples that stand in for the real thing.
  • General questions about how to do something, with no private data attached.

This is most of what owners actually want AI for. The sensitive list above is a small carve-out, not a reason to avoid the tool.

Set yourself up once

Two quick things make the whole habit safer:

  • Use a paid business account with training switched off. That way, even the safe stuff you do paste is not fed back into the model. We cover this in our guide on whether your data is safe with AI.
  • Tell your team the rule. If anyone else uses AI in your business, the “would I email this to a stranger?” test is the one sentence to share. It travels well and it sticks.

The bottom line

You do not need to be nervous about AI. You need one rule and a short list. Keep passwords, card details, other people’s personal data and confidential documents out. Anonymise everything else. Do that, and you get all the help with almost none of the risk.

If you would like to build these habits properly, alongside the practical AI skills that actually save you hours, that is what our AI Automation Masterclass in Manchester is for. Plain English, real examples, your own questions answered. Tickets are normally £20. This one’s free, a limited-time offer to launch the series.

And grab our plain-English safety and starter sheets from the free resources shelf, so the rule is always within reach.