August is the last month for safely moving large trees or for re-potting bonsai plants.
If you don’t do it now, you have to wait until next June to do it.
To re-pot a bonsai, remove it from its pot and gently tease out the outer 1/3rd of the root ball with a skewer or a metal knitting needle. Then re-pot it back into its old pot with some fresh bonsai potting mix.
To move large trees, dig out a root ball about 1/3rd the width of the height of the tree. For most non-native trees, you can get away with poor workmanship this month.
… So do it now.
Plant at the same height as it was before you started & water it in very very well.