Scope
I have added a note at the customer level, but the note is not getting displayed on the invoices that I import via Api call or bulk operation. Why?
Summary
If an invoice note is added at the customer level, subscription level, or standard invoice level, it's expected behavior by design that these notes will not be displayed on invoices generated via the Import_invoice API call or by import invoices bulk operation. You need to pass the value via this parameter "notes[note][0...n],“ in the API call or this column on the bulk operation sheet as mandatorily in order to display the note in the invoice.
Solution
When you are generating any invoice by creating a subscription or onetime charges, whether via API or the admin console, the invoice note that is added to the customer level or subscription level will be displayed on the invoice.
But if you are importing invoices via API call or Bulk operation then the generated invoice will not carry the invoice note added at the customer level or subscription level. To display the note in the imported invoice, you have to pass the note text in the parameter notes[note][0...n] mandatorily.
Please find more details on invoice parameters here.
Related articles and Documentation