I couldn't find any answer related to this issue, so I have to post it by myself.

I entered an invoice with zero amount by mistake, now I want to delete or modify it but the system won't allow me to do so.  I need to delete it because I need to use that invoice number for another invoice.

This invoice is shown as Paid automatically but it can not be found in "Receipt". 

When I tried to void or adjust the system message says "the transaction has to be adjusted manually".

Please help!  Thanks