Mental Health Parity Law: What Your Insurance Must Do

The mental health parity law is a federal law called the Mental Health Parity and Addiction Equity Act, or MHPAEA. It was signed on October 3, 2008, and it applies to plan years beginning on or after October 3, 2009. In plain terms, when a health plan offers mental health or substance use disorder benefits, the plan generally cannot make those benefits harder to use than its medical and surgical benefits. That covers copays, deductibles, visit limits, prior authorization, medical-necessity rules, and annual or lifetime dollar limits.

That is the core promise. It is also narrower than many people expect. Parity is not a rule that every plan must cover therapy, and it does not set a single national benefit. It is a comparison rule: whatever mental health benefits a plan does offer must be treated no more restrictively than the medical and surgical benefits it offers.

What MHPAEA actually requires

The law works by comparison. If a plan covers mental health or substance use disorder benefits, then the financial requirements and treatment limits for those benefits generally cannot be more restrictive than the ones that apply to medical and surgical benefits.

These are general rules, not a promise about any one plan. Plans vary, and the details of how a plan applies parity are worth checking with the plan itself.

What the law does not require

MHPAEA does not require a plan to cover mental health or substance use disorder benefits at all. A plan that offers no mental health benefit is not breaking parity by staying silent; parity applies only where the plan already offers those benefits.

There are also exemptions. MHPAEA does not apply directly to small employers’ group plans with fewer than 51 employees, to retiree-only plans, or to Medicare; CMS notes that its requirements reach small-group plans indirectly through the Affordable Care Act’s essential health benefit rules. There is also an increased-cost exemption that can apply in some cases. If a plan turns down a request or a claim, the plan should be able to explain which rule it is relying on.

The ACA adds a coverage floor for many plans

Separate from parity, the Affordable Care Act requires individual and small-group plans to cover ten essential health benefits, and mental health and substance use disorder services are one of them. All Marketplace plans cover them, including behavioral health treatment such as psychotherapy and counseling. Marketplace plans cannot deny coverage or charge more because of a pre-existing condition, mental health included, and cannot put yearly or lifetime dollar limits on essential health benefits.

That coverage floor matters because parity only compares benefits a plan already offers. The ACA is why individual and small-group plans offer mental health benefits in the first place. For a broader look at how coverage, self-pay and lower-cost options fit together, see how to pay for therapy.

The 2024 rule and the 2025 non-enforcement statement

A new parity rule was issued on September 9, 2024. It was meant to add detail to how plans show they are following parity, particularly for limits like prior authorization and network design.

On May 15, 2025, the Departments of Labor, HHS and the Treasury said they would not enforce the new provisions of that rule while they reconsider it. The 2008 law itself still applies. In practical terms, the core parity protections described above remain in place, but the rule’s newer requirements are on hold for now. If a plan or an employer cites the 2024 rule, it is reasonable to ask which parts are currently being enforced.

Asking for the medical-necessity criteria

A plan must give its medical-necessity criteria for mental health benefits on request. That is one of the most useful rights a person has when a claim is denied or a service is questioned.

Ask the plan in writing for the specific criteria it used and for the plan language that applies. Compare that with the criteria the plan uses for a comparable medical benefit. If the mental health criteria are stricter or harder to meet, that comparison is the heart of a parity question.

When a plan denies therapy

A denial is not the end of the process. The first step is usually the plan’s internal appeal. Read the denial letter for the deadline and the exact reason given, and ask for the criteria and the documents the plan relied on.

If the denial is about whether a therapist is in the plan’s network, the issue may be network rules rather than parity. In-network vs out-of-network therapy and superbills explains how plans handle out-of-network claims and what an itemized statement can do.

If the coverage is Medicare, the parity law does not apply, and the coverage rules are different. Does Medicare cover therapy? Mental health under Medicare covers what Medicare Part B pays for and how the 20% coinsurance works after the deductible.

For a denial based on medical necessity or on a limit that seems stricter for mental health than for medical care, the parity comparison can be raised as part of the appeal. Keep copies of everything: the denial letter, the plan’s criteria, the therapist’s notes or letter if the therapist is willing to provide one, and the dates of each contact.

Where to complain

Where to take a complaint depends on the kind of plan:

• Employer plan questions and complaints: the Department of Labor’s Employee Benefits Security Administration, through askebsa.dol.gov.
• Non-federal government plans: CMS handles parity questions.
• Insurance sold in your state: your state insurance department regulates it.

These offices handle plan and parity questions. For an individual case that may need legal advice, a lawyer or the state insurance department is the right place to ask; this is general information, not legal advice.

What goes wrong

A few misunderstandings come up again and again.

Assuming parity means every plan must cover therapy. It does not. Parity compares benefits a plan already offers. A plan with no mental health benefit is not required by MHPAEA to add one, though other rules such as the ACA may require coverage for some plans.

Assuming a denial is final. Plans have internal appeal processes, and a denial letter should explain the reason and the deadline. Ignoring the letter lets the deadline pass.

Not asking for the criteria. A plan must give its medical-necessity criteria for mental health benefits on request. Without those criteria, it is hard to see whether the mental health rules are stricter than the medical ones.

Confusing network problems with parity problems. An out-of-network bill or a thin network is a real problem, but it may be governed by network rules, the No Surprises Act or state law rather than parity. The fix and the complaint route can be different.

Missing the 2025 change. The 2024 rule’s new provisions are not being enforced while they are reconsidered. The 2008 law still applies, but a plan may point to the pause. Ask which requirements the plan is currently applying.

Waiting too long. Appeal deadlines and complaint windows are set by the plan, by law and by the agencies involved. Acting soon after a denial keeps the options open.

A short checklist before you call the plan

• Ask for the plan’s medical-necessity criteria for the mental health service in question.
• Ask which plan language and which rule the denial relies on.
• Ask for the deadline for an internal appeal and what the appeal should include.
• Compare the mental health limits with the medical and surgical limits in the same plan.
• Keep a written record of each call, the date, and the name of the person you spoke with.

Parity is a comparison rule, and the comparison is something a person can ask the plan to show. The plan may still say no, but it should be able to explain why, and there are routes to challenge that answer.