Company Car Logbook and Professional Secrecy: Must Doctors and Lawyers Name Patients and Clients?

Published on 09.11.2026

Logbook and Professional Secrecy

Anyone who also uses a business vehicle privately and does not want to tax the private use at a flat 1 % of the list price needs a proper logbook (Fahrtenbuch). According to settled case law of the Federal Fiscal Court (BFH), the logbook must name the customer or business partner visited. For doctors, lawyers, tax advisers and other professionals bound by secrecy, this collides with their duty of confidentiality, because even the fact that someone is a client or patient may be confidential.

An example: A general practitioner makes house calls every day. Her car belongs to the business assets, and she keeps a logbook. In the column “reason for the trip” almost every entry reads “house call”; she has not entered patients’ names because she is bound to secrecy. In a tax audit, the tax office rejects the logbook and taxes the private use at a flat 1 % of the list price per month. Should she have written the patient’s name in the logbook? (Fictitious case for illustration.)

In short: Plain-text names are not strictly required, but the person visited must remain verifiable for the tax office. According to the case law so far, professional secrecy does not lower the requirements for the logbook. A logbook with a neutral purpose and a client or patient number, together with an attached directory, appears viable. The Hamburg Fiscal Court allows redactions only within narrow limits, and an appeal on points of law is pending before the BFH.

This article explains when a logbook is worthwhile at all, what Section 102 of the German Fiscal Code (AO), the Federal Ministry of Finance (BMF) circular and the case law of the BFH and the fiscal courts require, and which arrangements work for doctors, lawyers, tax advisers and other professionals bound by secrecy on the current state of the law. It ends with a checklist and answers to the most frequent questions. The basics of confidentiality towards one’s own client are covered in the article “Confidentiality in Your Own Case”.

Overview: Which arrangement works and which does not?

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When does a professional need a logbook at all?

Where a vehicle used more than 50 % for business is also used privately, the private use must be taxed at 1 % of the list price per month under Section 6(1) no. 4 sentence 2 of the Income Tax Act (EStG). Under sentence 3, the actual costs attributable to private trips may be used instead if the total costs are proven by receipts and the ratio of private trips to other trips is proven by a proper logbook. For employees with a company car, corresponding principles apply under Section 8(2) sentences 2 and 4 EStG.

The tax authorities require a logbook kept contemporaneously and in a closed form. It contains at least the date and the odometer reading at the start and end of every business trip, as well as the destination, the purpose of the trip and the business partners visited. Professional secrecy concerns the last of these items: the tax office demands proof for the logbook method, while the professional may not disclose what has been entrusted to him.

Practical tip: First check whether you need a logbook at all. With a low list price or a high share of private use, the 1 % rule may be the simpler solution. Note the cap of the flat amount at the total costs, the so-called cost ceiling (paras. 18 to 20 of the BMF circular of 18.11.2009). Work out both options together with your tax adviser.

What do the law and the tax authorities say about the logbook and professional secrecy?

Does Section 102 AO protect against naming the patient or client?

The law contains no special rule for professionals bound by secrecy. It knows only the right to refuse to provide information under Section 102(1) no. 3 AO. It belongs, among others, to defence counsel, lawyers, notaries, tax advisers, auditors, doctors and psychotherapists, insofar as it concerns what was entrusted to them or became known to them in that capacity. It lapses if the person whose secret it is has released the professional from the duty of confidentiality (Section 102(3) AO).

Section 102 AO does not mention experts. Publicly appointed experts are bound by the criminal-law duty of secrecy in Section 203(2) sentence 1 no. 5 of the Criminal Code (StGB), but the wording does not give them a right to refuse information under Section 102 AO.

Section 102 AO protects against the tax office questioning the professional about what has been entrusted to him. In our assessment, however, it does not relieve him of the burden of proving the conditions of the more favourable logbook method. Whoever fails to provide the proof remains with the flat rate.

Does the BMF circular offer relief for doctors and lawyers?

The BMF circular of 18.11.2009 grants relief for commercial agents and couriers (para. 25), taxi drivers (para. 26) and driving instructors (para. 27). Doctors and other professionals bound by secrecy are not in this catalogue. It replaces the earlier circulars of 21.1.2002 and 7.7.2006 (para. 36).

Where the same customers are visited regularly, para. 28 allows the date, the odometer reading and the business partner’s number, provided that the partner’s name and address are kept under that number in a customer directory. The directory must be attached to the logbook. The rule is drafted with delivery traffic in mind. Applying it to a client or patient directory is, in our assessment, obvious, but it is not expressly regulated. If the tax office does not accept the logbook as proper, the 1 % rule applies (para. 30).

For doctors, the Frankfurt Regional Finance Office (OFD) requires the patient visited to be named. According to it, professional secrecy does not entitle a doctor to omit patients’ names. If the patient visited is missing as a business partner, the logbook is regarded as improper and the private use is valued at the flat rate. As the purpose of the trip, “patient visit” is in principle sufficient, provided that the patient’s name and address are given. We are not aware of any administrative rule under which doctors may merely number their visits and keep the names separately. The accessible version of the directive is, however, only an extract.

How do the BFH and the fiscal courts decide?

What does the BFH require of a logbook?

The BFH has described the requirements consistently since 2006. In principle, the logbook must contain the customer or business partner visited or, if there is none, the subject of the business activity. Mere place names suffice only if the customer clearly follows from them or can easily be identified from documents that need no supplementing. Abbreviations for frequently visited destinations are permitted if they are self-explanatory or explained on a sheet attached to the logbook.

In 2012 the BFH confirmed this and clarified that a street without a house number or customer name does not define the destination sufficiently. The details essential to a logbook must be entered in the logbook itself. A list prepared afterwards is not sufficient even if it is based on a diary. In the same year the BFH held that the minimum details cannot be replaced by other lists that are not contained in the logbook itself. The duty of secrecy of a professional was not at issue in the judgments of 16.3.2006 and 1.3.2012.

What did the fiscal courts decide on secrecy up to 2011?

In 2007 the Hamburg Fiscal Court held, for an auditor, that professional secrecy does not lower the requirements for a proper logbook. According to the headnote of the Munich Fiscal Court of 20.7.2007, the same principles apply to doctors as to other frequent drivers. In 2011 the Lower Saxony Fiscal Court decided that professional secrecy does not entitle a person to omit the purpose, destination and business partners visited. According to that decision, “patient visit” or “client visit” may suffice as the purpose if the name and address of the person visited are recorded in a directory kept separately from the logbook. For the first two decisions, only the headnotes are available.

May a lawyer redact client names in the logbook (Hamburg Fiscal Court, 13.11.2024)?

The Hamburg Fiscal Court recognises that a lawyer’s confidentiality under Section 43a(2) of the Federal Lawyers’ Act (BRAO) also covers the client’s identity. It permits redactions in the submitted logbook insofar as they are necessary to protect that identity. According to the court, place names, trips to one’s own law firm and trips to authorities without a link to a mandate may not be redacted.

The plaintiff had redacted the details of route and purpose for almost all trips. That was not sufficient, the burden of proof for the business purpose remained with him, and the court applied the 1 % rule. It allowed an appeal on points of law. Unlike the Lower Saxony Fiscal Court, which concerned a separately kept directory, the Hamburg case concerned redactions in the logbook itself.

What is the status of the appeal before the BFH?

An appeal on points of law against the judgment is pending before the BFH (as of 9.11.2026; case numbers VIII R 35/24 and V R 22/26). The questions to be clarified are whether a lawyer may submit a partly redacted logbook and whether an assessment is void if it applies the 1 % rule because no unredacted logbook with client names was submitted.

In our assessment, the line of case law is consistent: the yardstick is whether the tax office can verify the trip, and the customer or patient visited must be identifiable for that purpose. So far this verifiability has mostly been established through the name, which is why secrecy does not lower the requirement. The open question is therefore not whether, but how: do full names in a protected directory suffice, and can the tax office demand this directory despite secrecy?

How should a professional keep the logbook?

Is a client or patient number with a directory sufficient?

On the current state of case law and administrative practice, a viable approach appears to be an electronic logbook with a change log, a neutral purpose (“client meeting”, “house call”), place and route stated openly, and a client or patient number instead of the name. The BFH permits abbreviations if they are self-explanatory or explained on a sheet attached to the logbook, and the tax authorities expressly require the number directory to be attached. Lists outside the logbook do not replace the minimum details. Whether an attached directory meets this requirement has not been decided by the BFH, so a residual risk remains. The directory should therefore form part of the logbook documentation and be kept dated, unalterable and, in day-to-day use, accessible only to authorised persons.

This creates a conflict of objectives that the professional must decide consciously:

• Attach the directory: Proper form is best secured, but the full names reach the tax office with the logbook.
• Hand over the directory only on request: Secrecy is preserved, but the professional bears the risk that the logbook is not accepted because the numbers are not resolved.

In our assessment, “kept separately” means protection against access by third parties, not that the directory may be missing at the audit.

Practical tip: Decide before submission whether the directory will be attached or handed over only on request, and record the decision and its reasons in writing. Enter a neutral purpose together with the client or patient number.

How far may a lawyer redact?

If details in the submitted logbook are to be redacted, then, according to the Hamburg Fiscal Court, only what permits conclusions about the person may be redacted, that is, the name and, in the case of single mandates, the address. Places, courts, authorities and one’s own law firm or practice remain legible. Give the reasons for the redaction in writing and add details of the business purpose so that the trip is plausible even without the name.

When may the directory be handed over: consent and disclosure?

If the tax office demands the directory, it may be handed over only insofar as it is necessary to verify the trip, and only if the client’s or patient’s consent or a justification exists. Without a justification, professions covered by Section 203 StGB face the charge of unauthorised disclosure. In our assessment, the tension is best resolved by consent to disclosure for tax purposes, obtained early in the mandate or the treatment contract. On submitting neutralised documents in tax audits, see the section “Related conflicts”.

What if the tax office rejects the logbook?

If the tax office rejects the logbook, an objection must be lodged within one month of notification of the assessment (Section 355(1) sentence 1 AO). Referring to the pending appeal on points of law, you can apply for the objection proceedings to be suspended. Suspension means that the assessment remains open until the BFH decides. The tax authority may suspend the proceedings if that appears expedient for important reasons (Section 363(2) sentence 1 AO); there is no entitlement to it. If the objection is based on a legal question to be resolved in proceedings pending before the BFH, the proceedings are suspended for that reason (Section 363(2) sentence 2 AO). This does not apply where the tax was assessed provisionally (Section 165 AO). The pending case concerns a lawyer, so for other professionals the transferability of the legal question must be substantiated.

Practical tip: Note the one-month objection period from notification immediately. In the objection, cite the pending appeal with both case numbers (VIII R 35/24, V R 22/26) and apply for suspension of the proceedings.

Are there alternatives to the logbook?

Besides the 1 % rule (see the practical tip above), a vehicle held as private assets is an option, with business trips claimed individually. It triggers no private-use taxation, and the logbook rules do not apply because they relate to the private use of a business vehicle. The naming problem does not disappear, however, but shifts: every trip deducted as a business expense must be business-related (Section 4(4) EStG) and must be explained comprehensibly on request. Which details the tax office may demand for this in a given case has, as far as can be seen, not been clarified. A business vehicle that is not used privately also triggers no private-use taxation. In our assessment, however, proving non-use is demanding.

Which arrangements are not permitted?

It is not viable

• to supplement the logbook afterwards from a diary or a list of clients,
• to redact almost all entries or to enter only “business trip”,
• to redact place names, courts and trips to the law firm.

Anyone who relies on the Hamburg line as settled overlooks that it is a first-instance decision which the BFH may set aside or tighten.

Related conflicts: entertainment expenses, data access and the vehicle-log order

The same tension between the duty of proof and secrecy arises with proof of entertainment expenses, for which Section 4(5) sentence 1 no. 2 sentence 2 EStG requires a written statement of the place, day, participants and occasion of the entertainment and of the amount of the expenses, with data access in a tax audit (Section 147(6) AO) and with the use of findings about third parties (Section 194(3) AO). For tax audits of professionals bound by secrecy, the BFH has held that rights to refuse production also exist there and that the tax office may demand the necessary documents in neutralised form. Whether conclusions can be drawn from this for the logbook has not been decided by the BFH.

Another “logbook” concerns the order under Section 31a of the Road Traffic Licensing Regulation (StVZO) where the driver cannot be identified after a traffic offence. It records the driver’s name, first name and address, not the persons visited. Someone caught by a speed camera while visiting a client may remain silent as the person concerned (Section 46(1) of the Administrative Offences Act, Section 136(1) sentence 2 of the Code of Criminal Procedure), but must then expect a logbook order. As a witness in proceedings against another driver, he is entitled to the right to refuse to testify under Section 53(1) sentence 1 no. 3 of the Code of Criminal Procedure as long as he has not been released. Naming the client without release is a disclosure under Section 203 StGB which would be authorised only if a justification (Section 34 StGB) applied. Whether a threatened fine is a “danger” within the meaning of that provision is, in our assessment, doubtful. No decision on secrecy in connection with the logbook order is known.

Conclusion

Professionals bound by secrecy do not necessarily have to enter full names in plain text in the logbook, but the person visited must be verifiable. The arrangement provided for customer directories in para. 28 of the BMF circular, and compatible with the BFH case law on abbreviations, is the number or abbreviation in the logbook with a directory to be attached to the logbook. The Hamburg Fiscal Court allows redactions only within narrow limits. Whether the tax office can demand the directory despite secrecy will presumably be decided by the BFH. Until then, the logbook should be documented carefully, consents obtained, disclosure made only after a necessity check, and an objection lodged against any rejection.

Checklist: logbook and professional secrecy

1. Does a logbook make economic sense compared with the 1 % rule?
2. Electronic logbook kept contemporaneously with a change log, with date, odometer readings, place, neutral purpose and client or patient number for each trip.
3. Directory dated, unalterable, accessible only to authorised persons; record the decision on attaching it in writing.
4. Redact only the personal reference and give the reasons for the redaction in writing.
5. Obtain clients’ and patients’ consent to disclosure for tax purposes.
6. Hand over the directory only on request and after a necessity check.
7. Note the one-month objection period, refer to the appeal on points of law and apply for suspension.
8. Entertainment receipts and data access: keep client data separate, state participants only with consent.

Frequently asked questions

Must the patient’s name be in the logbook?

Not necessarily in plain text, but the patient must be identifiable for the tax office. The Frankfurt Regional Finance Office requires the patient visited to be named, and according to the case law so far secrecy does not lower the requirements. A patient number in the logbook together with an attached directory appears viable.

Is “house call” enough as the purpose of the trip?

As the purpose, “patient visit” is in principle sufficient, provided that the patient’s name and address are given. The entry “house call” alone is not enough: if the patient visited is missing, the logbook is regarded as improper under the view of the Frankfurt Regional Finance Office, and the 1 % rule applies.

May I as a lawyer redact client names in the logbook?

Only within narrow limits. The Hamburg Fiscal Court allows redactions insofar as they are necessary to protect the client’s identity. Places, courts, authorities and trips to your own law firm must remain legible. Anyone who redacts almost everything stays with the 1 % rule. The appeal on points of law is pending before the BFH.

Is a client number instead of the name enough?

On the current state of case law and administrative practice, this appears viable if the number directory is attached to the logbook (para. 28 of the BMF circular). Whether an attached directory meets the BFH’s requirements has not been decided by the BFH, so a residual risk remains.

What happens if the tax office rejects the logbook?

The private use is taxed at 1 % of the list price per month. Lodge an objection within one month of notification, refer to the pending appeal on points of law and apply for suspension of the proceedings. There is no entitlement to suspension.

Does this also apply to tax advisers and psychotherapists?

The right to refuse information under Section 102(1) no. 3 AO also belongs to tax advisers and psychotherapists. It does not relieve them of the burden of proving the conditions of the logbook method. The pending appeal concerns a lawyer, so for other professionals the transferability of the legal question must be substantiated.

Further reading: Confidentiality in Your Own Case: When Lawyers, Tax Advisers and Doctors May Disclose Client Secrets, Chamber Complaint, Criminal Report, Threat: What Professionals Should Do Now (10 Steps).

As of 09.11.2026. Case law and administrative instructions are taken into account up to that date. This article is not a substitute for advice in an individual case.

Attorney Dr. Johannes Fiala and the law firm in Munich advise doctors, lawyers, tax advisers and other professionals bound by secrecy on questions of confidentiality vis-à-vis the tax office, on keeping the logbook and on objections against its rejection. Dr. Fiala has published extensively on professional law and tax law. Please contact the firm without obligation to discuss your individual situation in an initial consultation.