Question:
I've just enabled the global invoicing reset for the new year. Now the number has been reset, like I wanted it to. But what happens now? If I want to reset it again, say in a year, what should i do?

Answer:

Once you have enabled Global Invoice Numbering Reset, it will reset the global numbers every year. When you were selecting this option, there should have been a warning, saying that you will not be able to undo the selection. You can still adjust the date when the reset is supposed to happen.