This bill, titled the "Closing the Contraception Coverage Gap Act," seeks to amend Title XVIII of the Social Security Act to provide comprehensive coverage for contraceptive items and services under the Medicare program. Its primary purpose is to ensure that Medicare beneficiaries can access these services without any cost-sharing, including deductibles, coinsurance, or copayments, starting January 1, 2027. The legislation specifically modifies Medicare Part B to include contraceptive items and services as covered medical services, defining them to align with existing Public Health Service Act guidance. This definition encompasses patient-centered counseling, ancillary clinical services like consultations, device insertion, and follow-up care, regardless of whether the services are explicitly for contraception. Medicare Part C (Medicare Advantage) plans will also be required to cover these services without cost-sharing. For prescription drugs, the bill amends Medicare Part D to include covered Part D drugs that may be furnished for contraception, ensuring they are covered without deductibles or other cost-sharing. The Secretary of Health and Human Services is authorized to develop quality measures for contraceptive counseling, care, and access to ensure high standards. Furthermore, the bill includes provisions to ensure that individuals dually eligible for Medicare and Medicaid receive coverage for contraceptive items and services that is at least as comprehensive as that provided under State Medicaid plans. The Secretary of HHS is tasked with an annual review to confirm this comparable coverage. Finally, the bill mandates several studies to assess contraceptive coverage. The Secretary of HHS will study prescription drug coverage for Medicare beneficiaries with disabilities and the potential for covering over-the-counter contraceptive drugs with no cost-sharing. The Comptroller General of the United States (GAO) will conduct studies on health plans not required to cover all FDA-approved contraception or waive cost-sharing, and on differences in contraceptive coverage for dual-eligible individuals.