When do you need an authorisation to transport goods in accordance with the Road Haulage Act?

You answered correctly. According to the German Road Haulage Act (Güterkraftverkehrsgesetz), an authorisation is required when you transport goods commercially, meaning as a business activity for profit. It does not matter how far you drive or what type of vehicle you use; the decisive factor is that the goods transport is done on a commercial basis. Transporting goods privately or for personal use does not require authorisation under this law. This is important for anyone planning to operate a transport business or offer goods transport services.