Want to move an acer

While it's dormant is the answer, so you might get away with it ASAP, though earlier in the year would have been better.

It will be a big job to dig out, though, if it's that large and age.

If you really have to do this, prepare its new planting hole well, then get a tarpaulin or old sacking and dig a trench away from the shrub,all round, then get as much of the rootball as you can out onto the sacking. Get it planted at once and water it well for the next year.

I think you are taking quite a risk here. Good luck.

Hi Mel
Late autumn/winter is generally considered best for moving trees & shrubs. Don't know just where you live in UK but the acer is probably already starting into growth for you so, if you can, you might be better to wait until the end of the year.

Acers have quite fibrous root systems, so I think you have a good chance of it surviving. However, as said above, it's getting a tinsy bit late to move it. Do it right now if you have to. But if you can wait another year, it might be worth preparing the tree in advance by digging around half of it about 1.5 to 2 ft from the trunk in order to sever the roots on one side before leaving it another year. what this will do is encourage the tree to produce a large number of fibrous roots close to the tree, which will increase it's chances of survival when you get round to moving it next year. When you move it, do make sure you replant it to the exact same depth as it was at before and get the tree out with as much soil attached as possible so as to preserve the finer roots, which are the important ones, not the big thick ones.