Ferries how can they tell if it's commercial?

juliusceasor

Hi,

Can someone explain how P&O would know if you are taking a van with seats for commercial or non commercial travel rather than tourist travel?

For instance you travel out empty and return with a product how would they know the outward travel was commercial as opposed to freight. On the return you may be carrying a product but how would they know it was not for personal use rather than commercial? If it is freedom of movement of goods and people throughout Europe.
The fare difference is minimal so my main question is really from curiosity having made a booking and the form asking the question.