Well I certainly wouldn't cut it back like that - you wont have a tree left if you do. Is that all it said Guest?

Is it the one sold as S.c.Kilmarnock? This is the most commonly sold form. This is often a weeping standard of various heights. In which case you should cut back the old growth , but not the tall standard bit, to 3 or 4 inches from the base about now. It will then produce nice new long growths over the season and should flower on them next Spring. I am about to do ours now that the catkins have finished.
The ordinary Goat willow (S.caprea) is a not very interesting shrub rather than a tree and again should be cut right back every year to encourage new growth on which the catkins appear.

Gosh Owdb we've had a 'Kilmarnock willow' for years and have never considered pruning it... It is growing next to the dyke at the front side of our house and weeps down to the ground. I suppose if you want it to look 'tidy and neat' you could clip it back but we never have.

Found that when we did not prune ours it began to creep along the ground and take over the surrounding area. In fact it even rooted as it went and I do not want a Goat willow thicket just there. It depends on what you want I suppose.

Has never crept along the ground or tried to root itself - mind you it is confined in the space it is in.