calculate sum totals from multiple lists in the same site

LukeSykes the simplest way to do this is to have a flow in Power Automate that, on a set recurrence schedule (for example twice a day at 10am and 4pm), get the items from your first list, Petty Cash for example. For each item in the list it adds up the number/currency amount and adds it to a variable.  You'd need to have parallel branches for each of the other lists and and a variable for each of vouchers, invoices etc. You would then have an action that creates a new item in your "overall sum" list using the values from each of the variables.

Rob
Los Gallardos
Microsoft Power Automate Community Super User