Hopefully, it will never happen. But, if I realize that I overdrew more than the correct amount from a UTMA account, or I realize an amount was mistakenly withdrawn from UTMA, what is the immediate corrective action that I can take?
If I just redeposit the money, exact to the penny, with a note on the check within a certain period take care of the issue — like it never happened?
Yes, just return the money to the account, and keep a record of what happened. In the unlikely event the account was deprived of any substantial earnings as a result of this money not being there, a fully proper response would be to restore that amount as well, although this may not be a requirement.