ChatGPT for fiduciaries: protect payroll, tax returns and accounts

October 30, 2026 · Zecretly

The short answer: Payroll lists, tax returns and annual accounts contain your clients' social security numbers, IBANs, salaries and addresses. With Zecretly, you replace that information on your own computer before ChatGPT or Claude drafts a letter or reviews a spreadsheet. At the "Strong" level, totals and ratios stay consistent, so the math still works.

What do accounting and fiduciary firms use ChatGPT or Claude for?

Rarely for the bookkeeping itself, often for the work around it:

• drafting a cover letter for a tax return or a polite payment reminder,
• answering a client's question by email,
• explaining an Excel formula or checking a payroll list for anything unusual,
• summarizing changes in the annual accounts in plain language for a client.

In each case the service needs the context, but not the real names, numbers and accounts.

Which information is sensitive?

A typical client file holds names of people and companies, addresses, Swiss social security (AHV) numbers, IBANs, customer numbers, salaries, amounts and dates. Zecretly detects these kinds of information and replaces them with placeholders like [PERSON_1] or [ADRESSE_1]. The protected copy sits next to the original, for example as Payroll.zecretly.xlsx. The original stays unchanged.

How do the numbers stay consistent?

That depends on the protection level:

• Normal replaces personal details only. Amounts and dates stay as they are.
• Strong (default) shifts amounts by a secret factor and dates by a few days. Totals and ratios stay consistent, but the real values are no longer visible.
• Maximum shows amounts and dates as placeholders only. The service can no longer do any math with them.

An example with made-up numbers: a payroll list has two salaries, CHF 6,200 and CHF 4,800, for a total of CHF 11,000. Say the secret factor is 1.07. The protected copy then shows CHF 6,634 and CHF 5,136, for a total of CHF 11,770. The ratio between the salaries is the same, and anyone checking the total gets a consistent result. When you restore the answer with Zecretly, the real salaries are back. Numbers that ChatGPT or Claude calculated are converted back as well.

How do I keep client files apart?

In Zecretly, files that sit directly in the same folder form a case file. They share placeholders, the factor and the date shift. So create one folder per client: the same person then gets the same placeholder in the payroll list, the salary statement and the tax return, and documents from different clients never mix. After 30 days a new case file starts, and the older one can still be restored. Learn more in How Zecretly works.

How should I phrase the request?

For restoring to work, the placeholders in the answer must look exactly like they do in the protected copy, square brackets included. If the service turns [PERSON_1] into "Person 1" or makes up a name, Zecretly can no longer find that spot. One sentence in your request helps. Two examples:

• "Write a short, friendly cover letter to [PERSON_1] about the tax return we filed. Leave all placeholders in square brackets exactly as they are."
• "Check this payroll list: does the total of the gross salaries add up, and does any value stand out? Leave the placeholders unchanged."

In the second example, the service calculates with the shifted amounts. Its result is shifted too, and only matches your real numbers after you restore it. Before restoring, take a quick look to make sure all placeholders are still there. If one is missing, the service usually rewrote the sentence, and you fill in the value by hand.

Are fiduciaries bound by professional secrecy?

Article 321 of the Swiss Criminal Code lists, among others, lawyers, notaries, doctors and auditors who are bound to confidentiality under the Code of Obligations. Fiduciaries and tax advisors aren't named as separate professions in the text. If you carry out audits, though, you may be covered.

Duties apply even without a criminal provision: your engagement letter usually includes confidentiality, and the Federal Act on Data Protection (FADP) applies to any processing of personal data. Article 9 of the FADP only allows outsourcing to a service provider if no legal or contractual duty of confidentiality prohibits it. In the EU, the GDPR sets similar rules. Check what this means for your firm with your legal advisor or professional association. For more on auditors, lawyers and doctors, see Professional secrecy and ChatGPT.

What can't Zecretly do?

Many receipts arrive as scanned PDFs. Zecretly doesn't reliably read scanned PDFs without a text layer or text in images, and PDFs lose their layout. Descriptions like "the manager of the garage in the village" aren't recognized as a person. And Zecretly doesn't find every value. So take a look at the protected copy before you upload it.

Sources

• Swiss Criminal Code (SR 311.0), Art. 321: fedlex.admin.ch, accessed October 30, 2026
• Federal Act on Data Protection (FADP, SR 235.1), Art. 9: fedlex.admin.ch, accessed October 30, 2026