Mr.Ramakrishna,
Firstly Cenvat Credit on Input service does not depends upon the kind of registration (i:e whether Centralized or Decentralized)
Secondly, IF INPUT SERVICE (OF WHICH U WANT TO TAKE CENVAT CREDIT) IS UTILIZED FOR THE PURPOSE OF PROVIDING SERVICES WHICH IS TAXABLE UNDER SERVICE TAX THEN NO ONE TO ONE CORRELATION IS REQUIRED AND CREDIT IS ALLOWED..
EXAMPLE :- Mr. A is providing 2 services "X" and "Y" (BOTH ARE TAXABLE SERVICES UNDER SERVICE TAX)
AND HE HAS UTILIZED INPUT SERVICE "C" FOR PROVIDING SERVICE "X"
SIMILARLY INPUT SERVICE "D" FOR PROVIDING SERVICE "Y"
NOW CENVAT CREDIT ON INPUT SERVICE "D" CAN BE UTILIZED AGAINST THE SERVICE TAX PAYMENT ON SERVICE "X" AS WELL AS SERVICE "Y"
SIMILARLY CENVAT CREDIT ON INPUT SERVICE "C" CAN BE UTILIZED AGAINST THE SERVICE TAX PAYMENT ON SERVICE "Y" AS WELL AS SERVICE "X"
THIS IS WHAT IS CALLED AS NO ONE TO ONE CORRELATION IS REQUIRED