Hello,
Does anyone know how to add tracking code to recurring invoices?
The same way as for any other transaction that accepts tracking codes. If you’ve created a tracking code under Settings, the dropdown box for Tracking code will appear whenever relevant:
thanks for the reply. I have tracking code created. But when I try to create new sales invoice, tracking code shows up. But when I try to create recurring invoice, tracking code box does not show… 
Ah, yes, I think this is a bug. The screen shot I posted earlier was from a recurring invoice created with an earlier version. With the current version, the Tracking code field does not show when creating a recurring sales invoice. I am elevating this as a bug.
Fixed in the latest version (17.4.51)
perfect…thank you…you rock