If you're using bookkeeping software, be sure to research its book - closing / closing entries feature, as it is handled differently depending on the software. (money.stackexchange.com)
So if you are preparing this report without the assistance of bookkeeping software, simply produce a total monthly expense number. (lawfirmsuites.com)
While you can record your transactions anyway you like, it is highly advisable that you invest in dedicated bookkeeping software. (smallbusinessesdoitbetter.com)