Set the invoice numbering (number ranges)

Open Settings, then Number ranges. A number range is the counting scheme for one kind of document in one year, for example invoices. It is created automatically when you issue the first document of a year.
Coming from another program? Under Kind choose the document, for example Invoices, and under Year the year.
Fill Prefix (the letters in front of the number), Digits (how many places the number has, padded with zeros) and Next counter (the number the next document gets).
Check the line Next number: below the fields. It shows exactly how the next number will look.
Choose Save. A saved range appears in the list below; to change it later choose Edit on its row.
If your new counter skips numbers, the app shows how many and asks for a reason of at least 10 characters. Invoice numbers must run without gaps, so confirm only when the gap is explainable, for example numbers issued in another program, then choose Confirm the gap and save.
Once a range has issued a number, its prefix and digits can no longer change, and the counter can never go backwards.