Should our PTO try to keep our other assets to a minimum? Some of the things that we have purchased have automatically become school property, while other items, for some reason, have remained PTO property. The school is who makes use of these items, so I'm wondering if all of it should be donated. It seems to me that anything that we claim as PTO property will only make filing our taxes that much harder.
Your "year" is the financial year within which you operate (fiscal year). It should be defined in your bylaws. For PTO's it's often June 30 - May 31 or July 31-June 30. Usually something that coincides with the school year but gives you a little time to close out your books.
The amount you carry over is up to your group. Many maintain a minimum balance to help kick off the next year as startup funds. That's a smart move and may be required in your bylaws.(I belong to two PTO's. One requires $1000 minimum, the other $2000 minimum.)
If you have EXCESS funds to be carried over beyond this, again it's your organization's decision. But you should be able to answer the question "Why?" Sometimes groups are saving for a big project like a playground or holding back money to pay for T-shirts that get ordered in the summer. Some groups give the teachers a supplies stipend that hits that first month. So funds may be reserved for a purpose.
Aside from instances like that, most of us tend to think the PTO funds should be spent in the year earned so as to benefit the kids/families that participated in the fundraiser.
Bottom line: your organization gets to make these decisions. But you shouldn't hold money just to have it. There should be a reason or a plan for holding excess funds.