In QRDA_III_CMS_EP_2014_IG_Vol 1.pdf section 2.4 Identifiers, The CMS EHR ID, also known as the CHPL ID, goes on to clearly state that "Group practices with multiple sites using several Certified products must submit all the CMS EHR Certification IDs"
In QRDA_I_CMS_EP_2014_IG.pdf section 5.1.1 General Header, there is no detailed guidanced.

This information may be difficult for the data submissionvendor / clinical quality measure engine calculator to gather or even know. The source CEHRT CHPL ID information is collected at the time of MU objective measure attestation, may we suggest that avenue as the better sourceof truth for this information.