You don’t say what kind of iris you have, but I’m going to assume they are bearded iris. It’s best to move them in late summer or early fall, when their bloom has ended and their growth slows down. If you must, you can move them in spring as long as you are careful to dig up a large ball of soil around them and replant them immediately. Do this when the plants are still short in early spring, long before bloom spikes begin to appear. If you wait until they are much taller, they might not bloom and could be stressed enough to do poorly all summer.