Found at Common Tasks > Billing > Miscellaneous charges (for one or more students).
For example, you may need to charge all the Choir students for a performance uniform; or all the Year 7 students for a music text book. You can search for that group of records and then enter the charge details. They will all be charged at once, saving you having to find each one and entering a charge individually.
This button differs from Bill all Tuition enrolments for music diary/other in that the 'Find' is done in the Students file, rather than the Tuition file. If you're billing for a music diary, you may want to charge some students TWICE (if they're learning two instruments), whereas if you're billing for a performance uniform, you would probably only want to charge each student once, regardless of the number of ensembles they are in.