No exemption from GTA to GTA is available. Your client is providing service of GTA under Forward Charge Mechanism. So it is his responsibility to collect GST on freight and deposit with the Govt. Under RCM, a person who bears the freight, is liable to pay GST on the amount of freight. This legal status is same irrespective of the fact whether it is pre-GST era or post-GST regime. However, if one GTA hires truck from your client, that is exempted. Under RCM first liability is either of Consignor or consignee and thereafter, liability is of GTA but under FCM GTA's liability comes first. For GTA working under FCM, an other GTA is a routine Service Receiver. Hybrid mechanism if adopted by GTA can create problem. GTA should either work under FCM or RCM.