my last invoice for 2016 ist the number 20160044. Now i will set a new period.
The first invoice for 2017001 above. If i create a new invoice and saved it the number will set automatic to 20160045.
Can i do something to change it?
Yes. After your first sales invoice of the year has been created and auto-numbered,
Edit it and change the number to 2017001. The next time you create a sales invoice, Manager will search for the highest existing number (now 2017001) and add to it, numbering the next invoice to be 2017002.