There's a common misunderstanding that left over funds in an organizations budget category at the end of the year roll over into the same organization's budget category the following year. I have a canned response I usually send to organization leaders when the question about roll over comes up. Granted, its a bit simplified but I think it gets the basic concept across to those less experienced in unit finances.
"Excess funds do not roll over within a budget category ... however any left over funds are still in the unit's (stake or ward) checking account and are available for spending allocation.
"At the end of the year, the software closes out the financial year and zeros all the budget allocations for the new year. Clerks then enter organization budget allocations for the new year as approved by priesthood leadership. Any left over funds from the prior year are still in the unit's bank account where the actual dollars reside. The budget is just a tool to manage the funds in that account.
"Think of it like your checking account at home. Each month you receive funds (paycheck, pension, etc.) into your checking account. You then prepare a monthly budget to spend the money from the account. You may end up spending a little more from one budget category and a little less from another but overall you make sure you don't deplete all the funds in the checking account. Then next month, you may adjust your budget categories up or down as needed making sure your overall spending does not exceed your income and overdraw your checking account.
"The unit budget operates in the same way. Our income arrives quarterly from CHQ into a single unit checking account. Instead of a monthly budget, we prepare a yearly budget to spend the the projected income making sure not to overdraw the unit's checking account. Organizations should adjust their budget request for the new year up or down based on anticipated expenses for the upcoming year. If you anticipate extra expenses for the upcoming year, then request a larger budget. If your prior year allocation was more than you will need in the new year, then request less. Clerks and priesthood leadership then review all the requested organization budgets to make sure the total does not exceed projected income plus any funds remaining funds from the prior year."