Fundraising income is often banked as a net amount. For example you may use a fundraising web site such as GiveALittle, which charges a fee before remitting the amount to you. These fees need to be put in your cashbook as expenses, and the donation amount will be accordingly higher.
Another common scenario is purchases from money collected in cash, for example extra bread or onions for that sausage sizzle that is going so well. That’s fine, but again, those expenses need to be entered in your system together with the gross amount collected from your sausage sizzle, not just the net amount.
Let us know if you need help with how to do this.