Private car business expenses must be documented internally, not via invoices, per Polish tax regulations.

The Supreme Court allowed the taxpayers' appeal, overturning the lower administrative court's decision that required invoice-based documentation for private vehicle business expenses. The taxpayers argued that using internal records and monthly cost summaries was sufficient to prove the business connection of fuel and parts costs, while the tax authority insisted on invoices as the only valid proof. The court ruled that the lower court's interpretation violated the system of the regulation and the legislative intent, which permits internal documentation to establish the link between private car use and business activities.