Simply put, SSAE No 18 is the standard which recodifies all the previous attestation standards. It is the culmination of the efforts to clarify the various standards for performing attestation engagements, which includes among many others, SOC 1 (commonly referred to as SSAE No. 16) and SOC 2 and SOC 3 (AT Section 101), into a single set of standards for the auditors.
The practitioners performing the attestation engagements for SOC reports will not notice very many material changes in the standards; however, there are a few key areas of emphasis worth noting for SOC 1 reports: