YOU WILL GET YOUR INTEREST ACCOUNTING CODE BY CLICKING

https://cbec-easiest.gov.in/EST/MinorHeadSelectionServlet

BUT YOU HAVE TO GO THROUGH

https://cbec-easiest.gov.in/EST/InputPageForEPaymentServlet

While making payment in aces payment gateway you could se the accounting code for interest against the category of service towards which you are paying.

thank you all, i have one more query, can i take input credit of precessing fee in service tax? 

Cenvat credit could be availed only on tax and duty portions mentioned in Rule 3 of Cenvat credit Rules. Service tax paid on processing fee if any could be availed but not of processing fee itself