Can I cut back acer?

No - best done early spring, though it depends on the plant to some extent, some can be cut in midwinter, during dormancy.

Thanks Bamboo.

I agree with Bamboo, but check through the winter. If it is mild up in your area, late winter would be best to prevent bleeding. This applies to other things you may want to cut back as well.

I would say any time after leaf fall when the weather is not too severe. As Doctorbob says, you want to prevent it bleeding (acers are very prone to this when the sap is rising)

Well I would have said February, Andrew, but the sap will have risen by then, so when its dormant, presumably December/early January for the Acer, then, Skillen.

Thanks everyone.