What You Should Never Hand to a Public AI
By Anis Hammouche·June 25, 2026
Three families of information never go into a public AI tool: your clients' personal data, the secrets of your business, and anything covered by a confidentiality obligation. The French data protection authority, the CNIL, lists the same families. For everything else, one rule: if an outsider could read it without consequences, you can paste it.
Three ordinary scenes, invented but familiar. A freelance graphic designer pastes an invoice to have the mandatory legal wording corrected. A small agency copies an angry client's email to get a polite reply. A consultant submits a contract clause to find out whether it is valid. Each saves ten minutes, and each sends the tool's provider information that does not all belong to them.
Why a public tool is not a vault
When you type into a public AI tool, you assume the text stays between you and the screen. In reality it goes to the provider's servers, and what happens to it depends on the plan and your settings. At Anthropic, on the Free, Pro and Max plans, you choose whether your conversations are used to train the models: if you accept, retention goes up to five years, otherwise it stays at 30 days. These rules do not apply to plans under commercial terms, such as Claude for Work or the API. This text was announced in 2025, with a deadline of 8 October 2025 for existing accounts. I re-read the page on 1 November 2026; the terms change, so check them in your account. To compare the settings of different tools, read what you paste into free ChatGPT or Claude.
The CNIL takes a nuanced position in its questions and answers on generative AI (in French). For non-confidential uses, a public AI tool can be fine if you switch off the provider's reuse of your data. As soon as you handle clients' personal data or sensitive documents, it writes that it "seems generally more appropriate and more secure" to favor on-premises solutions, or failing that a system hosted remotely under a precise contract with the host.
The three families never to paste
Third-party personal data. For the CNIL (in French), it is any information relating to an identified or identifiable person: a name, a postal or email address, a phone number, a voice, an image. A company's contact details, with a switchboard and a generic address, are not in principle personal data. The line is blurry for a self-employed person: the name of a craftsman, a coach or a consultant is the name of a person.
The secrets of your business. Negotiated rates, quotes in progress, a client's code, strategy, a prospect list. If a competitor would gain something from it, it stays out.
Information under a confidentiality obligation. A non-disclosure agreement signed with a client, professional secrecy, a clause in your contract. The CNIL recommends never sharing confidential information on a public AI tool, naming personal data, company data and data covered by a secret or by professional ethics obligations. Here the problem is not only a leak: you committed not to disclose. Re-read the clause in your contract to see whether pasting the text into a third-party tool counts as a disclosure, and when in doubt ask your client for their agreement.
Task by task: what you remove before pasting
You do not need to give up AI. It is enough to remove what identifies or what is protected, then read the result. Here are five tasks from different trades.
| Task | Who does it | What you can paste | What you remove first |
|---|---|---|---|
| Correct an invoice | Freelance graphic designer | The labels, the structure, sample amounts | Client's name and address, bank account number, invoice number |
| Chase an unpaid invoice | Small communication agency | The tone you want, the number of days late | Client's name, contract reference, exact amount |
| Check a clause | Freelance consultant | The clause, without the parties' names | The names, and anything covered by a non-disclosure agreement |
| Answer an unhappy client | Online shop | The gist of the complaint, the outcome you want | Name, address, order number, contact details |
| Prepare a session | Coach | The outline of the session and general themes | The name, and any detail about health, family or work that makes the person recognizable |
The most common trap is copy-pasting context: the email forwarded "so it can rephrase", the spreadsheet export "to check an error". A third party's data leaves with the rest. Serious anonymization replaces names, addresses, numbers and amounts with neutral markers like [CLIENT] or [AMOUNT], then you read the final text before sending it. Here is what the rule gives on a reminder sentence (a fictional example):
Before: Hello Ms Garnier, invoice no. 2026-041 for 1,840 € for the Boulangerie Garnier website is 21 days late.
After: Hello [CLIENT], invoice [NUMBER] for [AMOUNT] for [SERVICE] is [NUMBER OF DAYS] days late.
For ready-to-use reply templates, read Answer your clients faster with templates prepared by AI.
An AI's legal advice can be wrong and convincing
That leaves the clause question. Here the problem is what you receive. The CNIL points out that generative models are not knowledge bases: they produce the most probable result, which can be inaccurate while looking plausible. Courts have already noticed. Damien Charlotin keeps a database of court decisions in which a party relied on content invented by an AI, most often fake citations.
Use AI to understand a clause or prepare your questions, not to decide. Check the source of every article it cites, and have a lawyer validate whatever commits your business. The reflex is the same for figures: AI invents figures and sources.
Your pasting rule
A sentence you remember beats a charter you forget. Copy this template, keep it near your keyboard and apply it before each paste:
Before pasting, I ask myself three questions:
1. Does this text identify a person (name, address, email, phone, bank account number)? [yes / no]
2. Would a competitor gain something from it (rates, code, quotes, strategy)? [yes / no]
3. Am I bound in writing not to disclose it (contract, non-disclosure agreement, professional secrecy)? [yes / no]
A single yes: I remove what identifies or I do not paste.
Frequently asked questions
Should I avoid public AI tools? No. A public tool is fine for anything you could publish without consequences: an article outline, a rephrasing of a public text, a headline idea. The point is to sort what you paste, not to give up the tool.
Is a business plan enough for client data? It changes the terms, since it falls under a commercial contract (at Anthropic, those plans are excluded from the consumer rules), but it is not an authorization. Read the data processing agreement before putting clients' information in, and do not assume it is compliant. The CNIL advises favoring a controlled solution for personal data.
How do I know whether a piece of information is sensitive? Ask the three questions of the pasting rule. A single positive answer is enough to keep it out of the public tool or to anonymize it completely.
Can I paste a half-anonymized document? I advise against it. Partial anonymization can leave enough clues to find a person or a company, especially in a small market. Replace everything that identifies, or do not paste.
Sources
- CNIL, Les questions-réponses de la CNIL sur l'utilisation d'un système d'IA générative (in French)
- CNIL, Donnée personnelle (in French)
- Anthropic, Updates to Consumer Terms and Privacy Policy, 2025
- Damien Charlotin, AI Hallucination Cases Database
The next step is to hand off the reminder without exposing your clients: Automate the reminders for your unpaid invoices. I share this kind of grid in my newsletter, you can sign up right below.
