Reverse charge on maintanence or repair service

DEAR SIR,

My Client is a Service Provider and they are PARTNER SHIP FIRM. They are providng service in the Head of Maintanece or Repair Service. Our Service Receiver is Asking us to Charge 6.18% in our bill. Because they are Paying the balance in Reverse Charge mechanism. My Question is Whether it is applicable for Maintanence or Repair Service and if it is Applicable, What Shall we do, in our billing and how we show that in the Service Tax Returns.  Please Guide me in this thing.