The best time to make these changes is when the budget request forms for the next fiscal year come out in the fall. At this point, you can request a permanent reallocation of budget that will be automatically reflected in the budget for the next fiscal year. If the request is made later in the year, after the budget has already been created, the change can still be made but it will require a journal entry to be done in July of the new fiscal year to make this reallocation.
