What kind of Iris, Bram. If Bearded Iris, I would not cut the leaves down until they turn yellow.

Bearded,
Flag
& a small one.....not seen it for a while oops

I never cut the foliage down and in the spring I remove them only if they are really too tatty.

The dead leaves don't decay fast enough here, Sbg, and eventually bury the bulbs too deep. Maybe not as much of a problem in moister climates.