Add a calculate bill button near the "Recalculate bill" button
The re-calculate bill button is awesome BUT if someone was never billed in that period due to an error of some sort [I.E. They were never made active, etc.] then that button does not work and you have to calculate a bill manually. It would be awesome if after adjusting the meter readings as needed and making services active that you could then hit a button that would calculate their bill based on those changes that you just made.