In Ear Works, invoice numbers are assigned automatically in ascending order. Even if you delete an invoice, that number will not be assigned to another invoice again.
You can change the next invoice number to suit your needs from the Administration > Change Next Invoice Number menu. You need to have administrator permissions to do this.
By default, the next invoice number is the next number after the last invoice number. You can set this to a value larger than the last invoice number but never less than that.
After you change the next invoice number, all invoices will be issued with an incremented value starting from that.
If you want to change the invoice number only for one specific invoice, open the invoice and click the [...] button next to the Invoice Number field. You’ll see this screen:
If the invoice number you are trying to change to is already allocated you’ll receive a warning.