ISO certification (ISO 9462 for alpine, ISO 13992 for touring) is the baseline safety standard your bindings must meet—no exceptions. TÜV or TIS certification goes a step further. It means an independent third-party lab has tested the binding beyond the minimum ISO requirements, checking for consistency and durability under more demanding conditions.
You'll most often see TÜV certification on premium bindings, especially from brands targeting the German and Austrian markets where skiers tend to be particular about safety validation. It's not strictly necessary, and plenty of excellent bindings carry only ISO certification. But if you're comparing two similar bindings and one has TÜV certification, it's a reassuring sign of extra quality control.
For most resort skiers, ISO certification alone is sufficient. If you're a aggressive skier, buying at the high end, or just want maximum peace of mind, TÜV certification is a nice bonus—not a must-have, but a meaningful one.