What does “Vertrauenssache” mean in German?

At these flower fields, nobody guards the tulips. You cut your own and leave the money in a box. The farmer sums it up: “Der Verkauf ist Vertrauenssache” — selling here is a matter of trust. A Vertrauenssache is anything that works on the honour system: people could cheat, but usually they do not. No guard, no fence, no receipt — just trust.

“Der Verkauf ist Vertrauenssache.” — “Selling here is a matter of trust.” It joins Vertrauen (trust) and Sache (thing, matter). So a Vertrauenssache is literally a “trust-matter”: something that only works if people act honestly, since nobody is checking. The farmer adds that it has worked so far — people around here pay up, and he plans to keep the fields open. You will hear it for honour-system setups and private choices alike: “Trinkgeld ist Vertrauenssache” (tipping is a matter of trust), or “Wem ich das erzähle, ist Vertrauenssache” (who I tell this to comes down to trust). Usage note: it often describes something with no rules or guards behind it — it works because people choose to do the right thing.