The same groups that are subject to the employer mandate are subject to the IRC Section 6056 reporting requirements.
This includes applicable large employers (groups with 50+ FTEs) and applicable large employer members (groups under common ownership where the total among all of the members companies is 50 or more FTEs – called an aggregated applicable large employer group).
Self-funded companies, including companies with fewer than 50 FTEs, are subject to the Section 6055 reporting requirements.