Since 2014, under the Affordable Care Act, all new individual and small-group health insurance policies (including those sold in the ACA’s health insurance exchanges and off-exchange) must cover essential health benefits for all enrollees.
And there cannot be annual or lifetime caps on the amount of money the insurer will pay for the services (note that there can still be a cap on the number of covered visits; for example, an insurer might cover 20 physical therapy visits in a year, and that’s still allowed).
Those are broad categories of care, and it’s up to each state to define exactly what has to be covered under each essential health benefit category. States do this by designating a benchmark health plan (see definition 2 here). So although the ACA’s essential health benefit categories are the same in every state, the specifics of exactly what has to be covered by individual and small group health plans will vary from one state to another.
Prior to 2014, it was common for individual market plans in many states to not include maternity benefits, prescription drug coverage, or mental health/substance abuse coverage. But since 2014, all new individual major medical plans have included these benefits — along with the rest of the essential health benefits — for all enrollees.
Grandmothered and grandfathered plans are not required to cover the ACA’s essential health benefits, although grandmothered plans are required to cover recommended preventive care with no cost-sharing. Large group plans are also not required to cover essential health benefits (but if they do, they cannot impose dollar limits on the benefit), although they are required to cover recommended preventive care without any cost-sharing, unless they’re grandfathered.