TRICARE Index Definition & 2026 Cost Impacts
*Disclaimer: TRICARE.com is an independent reference site and is not the official TRICARE program. For official policy, please visit TRICARE.mil.*
## Definition In the context of TRICARE, an index is the set of standardized values or data points used to adjust annual premium increases, enrollment fees, and catastrophic caps.
## What it means in practice For most TRICARE beneficiaries, the "Index" refers to the annual cost-of-living adjustment (COLA) based on the retiree pay increase percentage. Each year, the Department of Defense uses this index to determine how much your out-of-pocket costs will rise. For 2026, these adjustments ensure that healthcare costs stay proportional to the military retirement pay increases.
If you are a Group B beneficiary (those who joined the military on or after January 1, 2018), your enrollment fees and copayments are almost always indexed. For example, if the retiree COLA index is set at 2.5%, your TRICARE Select enrollment fees and your Catastrophic Cap will likely increase by approximately that same percentage for the following plan year. These updates typically take effect on January 1st of each year.
The index also plays a role in provider reimbursement. TRICARE uses the Medicare Physician Fee Schedule as an index to determine the "allowable charge" for services. When Medicare adjusts its rates, TRICARE typically follows suit. This is why you may notice that a doctor’s visit copay stays the same, but the total amount TRICARE pays the doctor changes behind the scenes.
For 2026, beneficiaries in the West Region (managed by TriWest Healthcare Alliance) and the East Region (managed by Humana Military) should check their respective portals in October during Open Season. This is when the results of the annual indexing are published, showing exactly how much the Monthly Premium or annual deductible has shifted for the upcoming calendar year.
## Related terms * **Catastrophic Cap:** The maximum out-of-pocket amount you pay each year for TRICARE-covered services before the plan pays 100%. * **Cost-of-Living Adjustment (COLA):** The annual increase in Social Security and military retirement pay, which often serves as the index for TRICARE fee changes. * **Group B:** Beneficiaries whose initial enlistment or appointment occurred on or after January 1, 2018, and who are subject to indexed fee increases. * **Allowable Charge:** The maximum amount TRICARE will pay for a covered health care service, often indexed to Medicare rates. * **Open Season:** The annual period (usually November to December) when beneficiaries can change plans based on the new indexed rates for the following year.
## Sources * **TRICARE.mil: Cost Terms**: https://www.tricare.mil/Costs/Cost-Terms * **Defense Health Agency (DHA)**: https://health.mil/ * **TriWest Healthcare Alliance (West Region)**: https://www.triwest.com/