AI in a fiduciary office: what your client data allows.
A fiduciary office may use an AI provider for most client work, if the contract with the provider meets the Data Protection Act. Audit mandates and clients with a confidentiality clause need a stricter setup.
Which secrecy rules apply
The professional secrecy of the Criminal Code, Article 321, names lawyers, notaries, doctors and auditors bound to secrecy under the Code of Obligations, among others. Fiduciaries as such are not on the list. Auditors keep secret what they find in an audit, under Article 730b of the Code of Obligations, so audit work falls under the stricter rule.
For all other mandates, three rules apply. The Data Protection Act fines anyone who wilfully discloses secret personal data learned in a profession that requires knowing them, up to 250,000 francs. The Code of Obligations makes you liable for the faithful and careful performance of the mandate. And many mandate contracts contain a confidentiality clause of their own.
What an AI provider may receive
An AI provider that processes client data for you is a processor. Under Article 9 of the Data Protection Act you may hand it the data by contract if it processes them only as you could yourself and no statutory or contractual duty of confidentiality forbids it. You also have to make sure it can keep the data secure. Handing data to a processor without meeting these conditions carries a fine of up to 250,000 francs.
A provider on business terms, with a processing contract and no training on your data, covers ordinary bookkeeping, payroll and tax work. Audit data and data from clients whose contract forbids passing it on go to a model you run yourself, or stay out of AI tools.
Which client data is particularly sensitive
Salary and tax figures are not on the law's list of particularly sensitive personal data. Some documents in a fiduciary office still contain such data:
- Health data, for example in sick-leave records and accident reports in payroll
- Data on social assistance measures
- Data on administrative and criminal proceedings and sanctions
- Religious affiliation, where it appears in tax documents
Where AI helps in a fiduciary office
AI helps with the text work around the figures. The final figures stay in your accounting software, because a language model is strong with text and unreliable with exact sums.
- Sorting incoming receipts and documents by client and type
- Drafting client letters, reminders and explanations of a tax return
- Answering staff questions from the office's own templates, guides and past answers
- Summarising new circulars and rulings for the team
- Preparing the first draft of a document list for an annual closing
Who answers for the result
The fiduciary. An assessment on the TREUHAND|SUISSE blog from September 2026 says: the fiduciary remains responsible to the client for the careful performance of the mandate, also with AI. The AI may research or prepare a draft, the professional responsibility for the result stays with the fiduciary. Have someone who knows the file check every result before it goes to a client.
How to start
- List the kinds of data your team would give to an AI, mandate by mandate
- Mark audit mandates and contracts with a confidentiality clause
- Choose a provider on business terms for the rest and sign its processing contract
- Start with one task that comes up every week, such as client letters, and measure the time before and after
- Write the rule on one page, so everyone knows what may go where
Questions
Are fiduciaries bound by professional secrecy like lawyers?
Not under the Criminal Code, unless they work as auditors bound to secrecy under the Code of Obligations. The Data Protection Act's fine for disclosing secret personal data learned in a profession, the duty of care in the mandate and any confidentiality clause still apply.
May we put client bookkeeping into ChatGPT?
Into a business plan or the API with a processing contract and no training on your data, yes, if no confidentiality clause forbids it. Check where the provider processes the data and, for the United States, whether it is certified under the Swiss-US Data Privacy Framework.
Are salary data particularly sensitive?
No, salary figures are not on the law's list. Health data in the same payroll file, such as a sick-leave note, are.