GTA under RCM

Both. depending upon the GTA........... can charge forward charge otherwise RCM....

Charge of GST on services provided by GTA In terms of notification no. 11/2017-Central Tax (Rate) dated 28.06.2017 as amended by notification no. 20/2017- Central tax (Rate) dated 22.08.2017 , sr.no. 9 and sr. no. 11, (i) Services of goods transport agency (GTA) in relation to transportation of goods (including used household goods for personal use) (Heading 9965 &9967 respectively) attracts GST @ 2.5% or 6% CGST. Identical rate would be applicable for SGST also, taking the effective rate to 5% or 12%. However, the rate of 5% is subject to the condition that credit of input tax charged on goods or services used in supplying the service has not been taken. The Explanation to the notification further clarifies that it shall mean that,- (a) credit of input tax charged on goods or services used exclusively in supplying such service has not been taken; and (b) credit of input tax charged on goods or services used partly for supplying such service and partly for effecting other supplies eligible for input tax credits, is reversed as if supply of such service is an exempt supply and attracts provisions of subsection (2) of section 17 of the Central Goods and Services Tax Act, 2017 and the rules made there under. GST @ 6% CGST (12% cumulative) is subject to the condition that the goods transport agency opting to pay central tax @ 6% under this entry shall, thenceforth, be liable to pay central tax @ 6% on all the services of GTA supplied by it. Further, there is no restriction on the GTA from taking ITC if this option is availed.

Refer:  cbec/gst/goods_transport_service