Dear Bhanu, Last year there was no registrstion fees and this year too it is expected to be the same. If you are an M.Tech applicant, you should register for GATE COAP on the basis of your GATE score after applying to the IITs of your choice. You shpuld register at coap.iitm.ac.in.
Please go through this page for more information regarding the registration process:https://engineering-careers360-com.cdn.ampproject.org/v/s/engineering.careers360.com/articles/gate-coap/amp?amp_js_v=a2&amp_gsa=1&usqp=mq331AQCCAE%3D#referrer=https%3A%2F%2Fwww.google.com&amp_tf=From%20%251%24s&ampshare=https%3A%2F%2Fengineering.careers360.com%2Farticles%2Fgate-coap