How do invoice ID numbers work?
Harpoon uses a unique ID number to identify each of your invoices. By default the invoice ID numbers in your account will start at 1 and automatically increment by one with each subsequent invoice created.
But you have the freedom to override these invoice ID numbers with your own numbering system. The next time you create an invoice simply type your preferred invoice ID number into the Invoice ID number field. You can use any combination of letters, numbers, or hyphens for your invoice IDs. Whatever invoice ID number you choose Harpoon will automatically increment it by one for the next invoice created.
For example, if you type in “ABC123” as your invoice ID number, the next invoice you create will automatically have “ABC124” pre-filled in the Invoice ID number field. Likewise if you type in “123ABC” as your ID number, the next invoice would automatically have “123ABD” pre-filled.
Note: Please avoid using non-alphanumeric characters in your invoice ID numbers.
For more information on invoicing check out the Invoicing support articles.