we also do a budget for review in april and vote in may as our PTO year ends July 31st and the monies must be set before the new board takes office and our bylaws state the budget must be voted on at a general membership meeting and our last one of the year is in June. We do include carry over to last the summer and to start the next school year until the first fundraiser is done!
I agree with JHB and Critter, but we bring our budget to the organization for approval in June so it is approved for the beginning of the new school year.
For us, usually the summer or right before the beginning of school. It's up to the new crop of officers (elected May) to set the new budget, which must be presented at the August general meeting for approval.