Preface

When creating an invoice, the API facilitates two types of invoice-models. A regular invoice, with invoice data and multiple invoice lines data. A creditnote, that also has the same depth of invoice lines that can be refunded. The endpoint is available from an HTTP_POST at POST V2Invoices

Ground rules for creating an invoice

There are a couple of rules, that needs attention before we go into the further details.

The given amount should always be positive, both on the invoice and in the invoice lines.
An invoice has the InvoiceTypeCodeset to PIE
A creditnote has the InvoiceTypeCode set to PCM
Card payments can be done instantly, both payments and creditnotes.
PdfInvoice (optional) can hold your own PDF invoice layout and details. When absent, FarPay standard PDF invoice will be shown.
PdfAttachments (optional), append PDF documents to the PdfInvoice, in order of appearence in the attachment list.
An existing customer will only be referenced with CustomerNumber
New customer can be created when not identified by the CustomerNumber - But it is recommended that the Customers POST endpoint is used to create new customers.