Keyline knows about different kinds of invoices.
The most prevalent type are customer invoices which are invoices, that a printery sends to it's customers in order to bill them for products they manufactured as part of an order.
The usual workflow when interacting with customer and supplier invoices is, they get created, eventually updated. As soon as they're deemed final from an accounting perspective, they are either marked as 'billed' (in case of customer invoices) or 'checked' (in case of supplier invoices). Once invoices are either 'billed' or 'checked' they can't be changed or deleted anymore. Customer Invoices however, can be reversed, which effectively creates a negated version of the respective customer invoice.
All invoices types share certain fields and characteristics. Most important of these commonalities is that theu all have line items. Customer and Reversal Invoices also both have contacts and addresses.
Please note that the current version of the API is not suited to create invoices
that are based on orders. Currently, the preferred way to do this, is still via
the Web UI of Keyline.
If you want to do this via the API, then please reach out to us.