24 July 2010
You can also convince your auditor by showing him challan status through NSDL site's TAN based view. through following link--
https://tin.tin.nsdl.com/oltas/index.html
But if he insists on challan then you have to contact the bank. On payment of a certain fee they will provide you a cyber receipt. If your client had made e-payment then he can download duplicate challan through net banking.
24 July 2010
AGREED WITH EXPERTS. IF YOU PAY ONLINE TAX HIMSELF, THEN YOU CAN GET IT FROM OWN BANK ID. IF YOU PAID TAX THROUGH BANK, THEN YOU HAVE TO CONTACT WITH BANK. OTHERWISE , BY HELF OF OLTAS YOU CAN VIEW CIN NO.