Can I use ChatGPT, Claude & Co. with customer data?
ChatGPT, Claude, Gemini and Copilot are US cloud services. The moment personal data flows into a prompt, a third-country transfer to the US begins – with all the GDPR obligations German companies often underestimate. Anyone working without a data processing agreement or using the free version typically breaches the GDPR with the very first prompt.
With standard accounts and no additional measures, this is not GDPR-compliant.
- No DPA on Free/Plus/Pro tiers
- Data transfer to the US
- Professional secrecy can be criminally breached
ChatGPT, Claude & Co. – these are the tools
All four leading AI assistants are cloud services from US vendors. Every text you enter leaves your company and Europe.
Market leader from OpenAI. Inputs are processed in the US. Free and Plus accounts have no data processing agreement and may use inputs for model training.
Anthropic's language model. Hosted on AWS US. Standard accounts are not designed for processing personal data in German companies.
Google's language model. Inputs flow into the Google ecosystem. Entanglement with other US services amplifies the third-country issue.
Microsoft's AI assistant (built on OpenAI models). Even with an EU-based M365 tenant, the vendor remains subject to the US CLOUD Act.
Six GDPR questions cloud LLMs rarely answer cleanly
Anyone entering customer data into ChatGPT, Claude or Gemini typically trips over several of these at once.
No data processing agreement
Free, Plus and Pro accounts come without a data processing agreement. Without a DPA, passing personal data to the provider is already unlawful.
Third-country transfer to the US
Data lands on US servers. The EU-US Data Privacy Framework from 2023 is a political bridge whose legal certainty is being challenged again by privacy advocates and courts. The CLOUD Act remains untouched.
No solid legal basis
Real consent from your customers for processing by OpenAI or Anthropic is practically never obtained. Legitimate interest rarely outweighs the risks of third-country transfer.
Information duties unmet
Customers must be transparently informed that their data is shared with US LLMs – including recipients, third-country transfer and legal basis. In practice, no privacy policy says so.
Professional secrecy breached
Doctors, lawyers, tax advisors, pharmacists, insurers, banks: anyone feeding client or patient data into cloud LLMs can commit a criminal offence under § 203 StGB – punishable by fine or imprisonment.
Trade secrets exposed
Once contract drafts, prices, source code or strategies reach cloud LLMs, they typically no longer qualify as adequately protected under the German Trade Secrets Act.
Which customer data is especially critical
Anything that makes a person identifiable is personal data – names, email addresses, customer numbers, phone numbers, IP addresses. Even a single such field in a prompt triggers GDPR duties.
Special category data under Art. 9 GDPR – health, religion, ethnic origin, sexual orientation – should practically never enter cloud LLMs. The risk here is at its maximum.
Never enter into cloud LLMs
- Customer names, addresses, dates of birth
- Health or treatment data (Art. 9)
- Job applications, CVs
- Contract, pricing and condition data
- Source code with internal logic or credentials
- 1:1 email threads with customers
- Client, patient or mandate data
What can happen when it goes wrong?
GDPR fine
Or 4 % of global group turnover. The higher amount applies (Art. 83 GDPR).
Damages
Every affected person can claim non-material damages – even without concrete proof of harm.
Criminal liability
Professionals with secrecy obligations face personal fines or imprisonment in addition to corporate sanctions.
Reputation
Published fines and privacy incidents remain visible in search engines and trade press for years.
How to use AI in business safely?
Three paths – ranked by protection level. The strongest option is the one where your data never leaves your premises.
On-premise AI – data stays in-house
AI that runs on your own hardware. No third-country transfer, no DPA needed, full access to internal sources without compliance risk.
- No data leaves your network
- GDPR out of scope (no external processor)
- Suitable for § 203 professions
EU-hosted AI vendor with DPA
Specialised European vendors hosting in the EU, offering a DPA and transparent training policy. Lower risk, but ongoing checks needed.
- Verify the DPA and EU hosting
- Opt out of training on your inputs
- Check the parent company and CLOUD Act exposure
Consistent anonymisation
If cloud LLMs are unavoidable: strip personal references before the prompt. Replace real names with placeholders, omit addresses, no plain text from contracts.
- Clear usage policy across the company
- Train employees
- Residual risk remains – re-identification possible
FAQ – the most common detailed questions
ChatGPT Enterprise offers a DPA, no model training on your inputs and EU data processing as an option. That is much better than the Plus variant. The core problem remains: OpenAI is a US corporation, and the US CLOUD Act allows US authorities to access data. A GDPR data protection impact assessment is mandatory, and for special category data or § 203 professions Enterprise is usually not sufficient.
Sources & further reading
This page draws on the following public and official sources:
- DSK – Orientierungshilfe zu Künstlicher Intelligenz und Datenschutz (Mai 2024, PDF)
- DSK – Technische & organisatorische Maßnahmen für KI-Systeme (Juni 2025, PDF)
- EuGH – Urteil C-311/18 „Schrems II" (16. Juli 2020)
- EU-Kommission – EU-US Data Privacy Framework (Angemessenheitsbeschluss Juli 2023)
- EDPB – Empfehlungen zu ergänzenden Maßnahmen bei Drittlandstransfers
- BfDI – Informationen zu Künstlicher Intelligenz und Datenschutz
- EUR-Lex – Verordnung (EU) 2016/679 (DSGVO) im Volltext
Sovereign instead of risky
KOSMO runs on your own hardware or in sovereign EU data centres. No US cloud, no third-country transfer, full control.
This page provides a general overview and is not a substitute for legal advice. For specific cases – especially involving special category data or professional secrecy – consult your data protection officer or a specialised law firm.
