How does the Xero Invoice Number get populated?

The Invoices API endpoint has a InvoiceNumber element which is a unique alpha numeric code to identify an Invoice. You have 2 options when uploading Invoices to Xero:

1. leave this blank and Xero will will auto-generate this from your Organisation Invoice Settings
2. populate this with a value from a FileMaker field

In the fmAccounting Link (Xero Edition) file we are using the 2nd option to populate this with the value from the InvoiceNumber field (an auto-enter serial number field). If you wish to change this to have Xero auto-generate the number for you just comment out this line:

["InvoiceNumber" ; Invoices::InvoiceNumber; JSONString];

in the Create Invoice in Xero script when it sets the $json variable with this value.

We have a separate field in the Invoices table named XeroInvoiceNumber which we populate with the Xero Invoice Number value, regardless of the above settings.