checked 3 months total compared to monthly total and it doesn't add up ?

Hi, the billing result for a custom date range is calculated using the current billing rules. Monthly bills, however, are generated using the billing rules that were in effect at that time and are saved as fixed records, so they will not change if the rules are updated later.

This may explain the difference you’re seeing. Could you please confirm whether the billing rules used during those three months are the same as the rules currently configured?