When you mark an invoice as paid on the invoice list, it always prompts you to create an income record - regardless of any settings on your order form. The auto create income setting on the order form is to stipulate that if/when a callback is received from a payment service provider to say that the payment was completed successfully, it should then automatically create the income record and mark the invoice as paid without any manual intervention from you (although this might not be working for you if you have pending until paid turned off as indicated in your
next post).
To fix the problem with the currency not being picked up from the invoice, please first upgrade to version 2.0.9, then replace the following files with the attached versions:
/administrator/components/com_nbill/framework/ajax/nbill.ajax.invoice.php
/administrator/componnets/com_nbill/admin.html/income.html.php
/administrator/components/com_nbill/admin.html/expenditure.html.php
[attachment deleted by admin]