I suppose you can treat Cannas the same as Dahlias. After the growing season dig up all the rhizomes, wash them and keeps them over winter in a shed.

I've also heard that you can overwinter them as I do with my banana plant... Apply a protective layer of mulch, the main trunk will die back in the winter and the plant will come up again from the rhizome in spring.

I leave mine in their pots and bury them under a few inches of woodchip. Much the same result. The only thing is that the roots kept growing last year, so I had to cut the pots off in the spring! I personally think they're tougher than most dahlias

A big part of it is the size of the rhizome and the soil drainage. If the Canna has a small or no rhizome then it is unlikely to make it through our long winters and you are better to leave it and mulch heavily. Large rhizomes can be lifted and stored and do so well.

The problem with leaving Canna in the ground is that it takes an age to resume growth in late spring, assuming that they survive the winter.

I lift all my large Canna (musifolia), cut off all apart from 6'' of growth and all the roots then place in fresh soil and I store in a crate to stop mould. I spray the roots with water every so often.

They are in large pots and the rhizomes were about 6" long when I got them this spring.
So I'll let them die back in the pot, clean off the old compost repot and keep frost free. Must say the foliage was pretty but no flowers.

oops sorry forgot my manners. Thanks for the advice.

Ive grown 65 from seed this yr,so im now in the process of digging up and storing in the shed,imjust going to brush the soil off,place in plastic tubs and hope.
Ive collected seed from some up to now so hopefully all wont be lost.

@Joolz68 - hope for a short spring as seed grown Canna are poor at surviving a 5 month winter and you may lose a majority. They are super easy from seed to make up for that.