Digital logbook: Tax-compliant record-keeping & the most common mistakes (Austria & Germany)

Keeping a mileage log is one of the least popular administrative tasks in a vehicle fleet – and at the same time one of the most prone to errors. Anyone who uses a company car for private purposes and wishes to claim the actual costs rather than the flat-rate tax allowance has no choice but to keep a properly maintained mileage log. However, there is often uncertainty, particularly regarding the digital version: will the tax office even accept it? What must it contain? And what errors could lead to a logbook kept for years being rejected in the event of an audit?

This article provides a practical overview – with a focus on the requirements in Germany and Austria.

21 May 2026

Why the logbook method matters

Anyone who uses a company car for private purposes must pay tax on this non-cash benefit. The simpler method is the flat-rate 1 per cent rule (Germany) or the non-cash benefit (Austria). It requires no record-keeping, but is often more expensive than necessary – particularly for vehicles used predominantly for business purposes.

The logbook method allows you to pay tax only on the actual private portion. This requires that all journeys – both business and private – are documented in full and in a traceable manner. Those who do this correctly often pay significantly less. Anyone who makes mistakes risks the tax office rejecting the logbook entirely and reverting to the more expensive flat-rate taxation – in the worst case, with retroactive effect.

In Germany, digital logbooks are subject to the GoBD (Principles for the Proper Maintenance and Retention of Books, Records and Documents in Electronic Form). These stipulate that all tax-relevant data must be stored in a way that is tamper-proof, complete and traceable.

In practical terms, this means the following for a digital logbook:

• Timely recording. Journeys must be entered promptly – subsequent additions from memory are not permitted. As a guideline, this should be within seven calendar days.
• No silent changes. Subsequent corrections are generally possible, but must be transparently documented – stating the original entry, the new entry and the date of the change. A system that allows entries to be overwritten without a trace does not meet the GoBD requirements.
• Tamper-proofing. The system must technically ensure that entries cannot be altered without being noticed. A simple Excel spreadsheet does not, in principle, meet this requirement – it is therefore not eligible as a GoBD-compliant logbook.
• Retention obligation. In Germany, logbook data must generally be retained for ten years, in a format that remains readable and verifiable even after several years.

Important to note: The tax office does not pre-certify software providers. The compliance of an electronic logbook is always assessed on a case-by-case basis – in cases of doubt, by a tax inspector on site.

A logbook does not have to be perfect. The tax office may overlook minor shortcomings. Problems arise when errors occur systematically or the overall picture presented by the records appears implausible. In practice, these errors most frequently lead to rejection:

1.Gaps in the records: Missing weekends, holiday days without entries or individual journeys that cannot be reconstructed retrospectively – such gaps immediately raise doubts. The tax office compares the documented mileage with the actual odometer reading (e.g. from garage invoices or MOT reports). If these do not match, the logbook is generally beyond redemption.
 

2. Vague journey details: “Client visit” without a name or address, “External appointment” without specifying the destination – this is not sufficient. Business journeys must be documented in such a way that they are traceable and verifiable. Generalised entries are regularly challenged during audits.
 

3. Retrospective corrections without a log: Anyone who changes entries retrospectively without the system documenting this change does not meet the GoBD requirements. This also applies if the correction was factually correct.
 

4. Excel spreadsheets or uncertified tools: A spreadsheet created by the user, which can be edited at will, does not meet the requirement for tamper-proofing. Apps or software solutions that do not maintain a traceable change history may also fail an audit – regardless of how neat the entries appear.
 

5. Mileage does not match the odometer readings: This error may sound trivial, but it occurs regularly: the mileage totalled in the logbook does not match the actual odometer readings as shown on garage invoices, tyre change receipts or MOT reports. Anyone who fails to check this regularly risks having their application rejected outright.

What a certified digital logbook must be able to do

A professional digital logbook solution takes care of most of the work – whilst also preventing the most common sources of error. The overview page for Rosenberger Telematics’ digital logbook solution shows the hardware options available for automatic journey recording – from OBD dongles to permanently installed solutions. 

The key features of a solution that complies with tax authority requirements:

• Automatic GPS tracking: Journeys are recorded in full without the driver having to take any action. Start point, destination, mileage and time are automatically logged.
• Tamper-proof: Entries cannot be altered without being noticed. Any corrections are logged with a timestamp and the original value.
• Clear separation of private and business use: The driver categorises journeys via the app – private journeys are visible only to the driver, not to the employer.
• Audit-proof archiving: Data is stored long-term, can be exported and is kept available in verifiable formats (e.g. PDF).

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A digital logbook is compliant with tax authority requirements if it is kept in a complete, timely, tamper-proof and traceable manner. The most common errors arise not from malice, but from a lack of knowledge of the requirements or from the use of unsuitable tools. By opting for a certified telematics solution, you eliminate critical vulnerabilities – whilst also saving time when maintaining the logbook on a daily basis.

Would you like to know whether your current logbook meets the requirements? 

In a free consultation, we’ll show you how the Rosenberger Telematics logbook solution works in practice – and which requirements it meets for Germany and Austria.

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Note: This article provides a general overview of the current requirements (as of April 2026). It is not a substitute for tax advice. In individual cases, it is advisable to consult a tax adviser.

Related topics: Digital logbook | Fleet management | Digitale tachograph