The Affordable Care Act requires health plans provide certain benefits beginning Sept. 23. But a "grandfather" provision in the bill preserves employer-sponsored health plans that existed on or before March 23, and excludes them from making significant changes.

The federal government states it is allowing these plans to maintain their grandfathered status because large employer-based plans "already offer most of the comprehensive benefits and consumer protections that the Affordable Care Act will provide to all Americans this year – such as preventing lifetime limits on coverage – and in the future." As a result, 133 million Americans with health coverage through large employers will see no major changes to their plans.

Under the new health care reform law, grandfathered health plans will be able to make routine changes to their policies and maintain their status. There are however specific changes that would cause these plans to lose their grandfathered status: