The most important consideration when selecting a SaaS vendor for a business process is whether the vendor' s information security certification is issued for the specific scope of the service that the organization needs. A certification that covers the entire vendor organization or a different service may not be relevant or sufficient for the organization's security requirements. The certification should also include industry-recognized security controls, be issued within a reasonable time frame, and be easily verified, but these are not as critical as the scope.
References = CISM Review Manual, 16th Edition, page 1841; 5 Top SaaS Security Certifications for SaaS Providers