Ask the Accounting Community

I am hoping someone can help me with a few questions regarding nonprofit accounting.  We have a small nonprofit corporation which we accept donations for a Community Day event.  If we do not expend all of the money that was contributed for the year by the end of the year, is there a issue with this?  Is there more paperwork we would need to fill out because of this?  Also, if the IRS was to audit our small nonprofit, would it require us to have original receipts?

 Thanks for any help on this.