The Central Board of Excise and Customs has clarified that, an Input Service Distributor (ISD) cannot accept any invoices on which tax is to be discharged under reverse charge mechanism, because the ISD mechanism is only to facilitate distribution of credit of taxes paid. The ISD itself cannot discharge any tax liability (as person liable to pay tax) and remit tax to government exchequer. If ISD wants to take reverse charge supplies, then in that case ISD has to separately register as Normal taxpayer.
Read more at: http://www.cbec.gov.in/resources//htdocs-cbec/gst/InputServiceDistributorinGST.pdf