What is the 20/20/20 rule in a military divorce?
A former spouse who meets all three twenties keeps TRICARE and commissary and exchange privileges after the divorce, in their own right. The three conditions, from the federal statute: the marriage lasted at least 20 years, the servicemember performed at least 20 years of service creditable toward retired pay, and those two periods overlapped by at least 20 years.
All three, not two of three. A 22-year marriage overlapping 18 years of service does not qualify. This is a hard-edged federal rule, which at least makes it one of the few divorce questions with a checkable answer.
The fine print that decides real cases
The overlap is the condition that fails most often. Count only the years you were married while the member was performing creditable service. Marriage before enlistment and marriage after retirement do not count toward the overlap.
TRICARE, and only TRICARE, is conditioned on not having employer-sponsored coverage of your own. Enroll in an employer plan and TRICARE eligibility under this rule is suspended while that coverage lasts. Your commissary and exchange privileges are not touched by it: those ride on the three twenties alone, so taking a job with health insurance does not cost you the base.
Remarriage ends it. Like several other former-spouse benefits, this one does not survive a new marriage, and here it does not come back either. If the later marriage ends in divorce or death, TRICARE stays gone, which is not how a survivor annuity works.
There is a one-year consolation version. The 20/20/15 rule: same 20 years of marriage and 20 of service, but an overlap of only 15 to 19 years, gives a former spouse one year of TRICARE from the divorce, a bridge rather than a lasting benefit. And failing both twenties is not the end of coverage: CHCBP, the military's COBRA equivalent, offers premium-based continuation for 36 months, indefinitely extendable for some unremarried former spouses receiving a pension share. That one has a hard deadline on it. You have to elect CHCBP in writing within 60 days of losing TRICARE, and if you miss it there is nothing to fall back on, including the indefinite extension, which can only be reached from coverage you already hold. (Decrees from before April 1985 under the old rule kept more.)
What this rule does not cover
It is a benefits rule, not a property rule. Division of the military pension itself runs under a different federal law (USFSPA) through the state court, with no ten- or twenty-year requirement for the division itself, and the widely repeated "ten-year rule" for pensions is only about whether DFAS pays your share directly rather than through your ex. How the pension actually divides has its own page. Do not let anyone tell you a short marriage means no pension share.
Update DEERS either way. The member must report the divorce, and an ex-spouse who no longer qualifies but keeps using TRICARE will face recoupment of claims paid, usually back to the divorce date.
If you are close to a threshold
Timing a divorce around a benefits cliff is a real and legitimate conversation, the same as the ten-year Social Security rule. If you are at 19 years of overlap, the difference between filing now and filing after the anniversary can be lifetime health coverage. Raise it with an attorney who handles military divorce specifically, because the interaction between state divorce timing and federal benefits rules is exactly where generalist advice fails.
The health insurance picture for civilian plans is its own page.
The 20/20/20 and 20/20/15 rules are federal (10 U.S.C. §1072) and do not vary by state; nearly everything else in a military divorce, from pension division to residency rules for filing, has its own specialized law. If service is part of your marriage, find an attorney who does military divorce regularly.