Medigap (also called Medicare Supplement) is private insurance that pays for what Original Medicare leaves behind. Original Medicare covers 80% of approved Part B services after the deductible; Medigap covers most or all of the remaining 20%, plus the Part A hospital deductible, hospital coinsurance, SNF coinsurance, and other gaps. Without Medigap, Original Medicare has no annual out-of-pocket maximum - your 20% can grow unlimited during a serious illness.

Federal law requires every Medigap plan letter to provide identical benefits regardless of insurer. Plan G from Aetna covers exactly the same services as Plan G from Humana - by federal regulation. This means you shop on price and customer service alone, not benefits. Premiums vary widely: same Plan G in the same ZIP code can range $130-$280/month depending on insurer's pricing structure (community-rated vs issue-age vs attained-age) and brand.

After your 6-month window closes, switching plans or getting Medigap for the first time requires medical underwriting in 47 states. Insurers can review your medical history and either deny coverage entirely, charge a substantially higher premium, or impose a 6-month waiting period for pre-existing conditions. Common conditions that lead to denial: diabetes with complications, history of cancer in the last 2 years, COPD, recent heart attack or stroke, uncontrolled hypertension. Once denied by one carrier, you remain insurable elsewhere - but pricing reflects your full medical history.

Part D plans are sold by private insurers under contract with CMS. Each plan publishes a formulary - the list of covered drugs and their tier placement. Tier 1 (preferred generics) costs the least; Tiers 4-5 (specialty drugs) cost the most. Medications not on the formulary require a formal exception request - and the plan can deny.

The 2026 Part D structure has four phases. (1) Annual deductible: up to $615 (some plans set $0). (2) Initial coverage: you pay 25% coinsurance until total drug costs reach catastrophic threshold. (3) Catastrophic: $0 cost-share for the rest of the year, after you've personally paid $2,100 out-of-pocket. (4) The donut hole was eliminated in 2025; there's no longer a coverage gap.

Pharmacies have tiers too. "Preferred" pharmacies have the lowest copays under each plan. "Standard" pharmacies are covered but with higher copays. Out-of-network pharmacies are not covered. Mail-order pharmacy is almost always preferred - 90-day supplies at the lowest tier copay. For maintenance medications, mail-order saves $5-30 per fill compared to retail.

Medicare Advantage plans contract with specific provider networks - typically a hospital system and its affiliated physicians. Your in-network PCP can refer to in-network specialists; out-of-network specialists require either OON cost-share (PPO) or no coverage at all (HMO). The hospital affiliation matters enormously: if your PCP only admits to a hospital not in your network, every hospitalization triggers an out-of-network situation that may cost tens of thousands.

Networks change throughout the year. Provider contracts renew, hospital systems merge, individual physicians retire or leave practices. Your plan must notify you in writing of provider changes affecting you, but notices are easy to miss. The provider you confirmed in October may be out-of-network in February with no fault of yours - and you discover only when the bill arrives.

Three things determine MA practice fit: (1) the specific plan name (not just "Humana" - the exact contract H-number, e.g. "Humana Gold Plus H1036-001"), because each plan has its own network; (2) the hospital affiliation of every PCP you consider; (3) the after-hours protocol - does the practice have an on-call line for in-network ER guidance, or do they default to telling you to go to the nearest ER (which may be out-of-network)?

Prior auth requests come from your provider, not you. Your provider's office submits clinical documentation supporting medical necessity. The plan reviews - sometimes by clinical staff, sometimes by AI-assisted screening tools. If the plan's criteria are met, approval is issued for a specific date range and provider. If criteria are not met, denial is issued - you have appeal rights but the procedure cannot proceed without authorization.

Approvals are highly specific: a specific provider, a specific procedure code, a specific date range. Going outside the approved window or to a different provider voids the approval. If your knee surgery is approved for June 15-30 with Dr. Smith, and you reschedule for July 5 with Dr. Smith, you need a NEW prior auth.

Denials trigger your appeal rights. The first level (plan reconsideration) is decided by the plan within 30 days for standard or 72 hours for expedited. If denied again, the case goes to an Independent Review Entity (IRE) - a CMS contractor not affiliated with your plan. IRE reverses about 25-30% of plan denials. Beyond IRE: Administrative Law Judge hearing (about $190 minimum amount in controversy threshold), Medicare Appeals Council, federal court.

The prudent layperson standard is your protection: if a reasonable person without medical training would have thought "this could be a heart attack," the ER visit is covered as emergency - even if the final diagnosis is heartburn. The plan cannot retroactively deny based on the diagnosis. But documentation matters: be specific about your symptoms in the medical record ("crushing chest pain radiating to left arm, shortness of breath") rather than vague ("chest discomfort").

Urgent care is the middle setting: not an emergency, but can't wait until a routine appointment. Examples: probable UTI, severe cold, minor laceration needing stitches, sprain, possible cellulitis. Most MA plans cover in-network urgent care at copays $40-75. Out-of-network urgent care is often NOT covered - verify before going. Walk-in clinics inside pharmacies (CVS MinuteClinic, Walgreens Health Corner) sometimes count as in-network primary care, sometimes urgent care, sometimes neither.

Office visits are routine illness, follow-up care, medication refills, chronic condition management. Most MA plans now cover telehealth at $0 or low copay - often the cheapest care setting available. Same-day office appointments are often available if you call in the morning, which is faster than an urgent care wait. The hierarchy from cheapest to most expensive: telehealth, office visit, urgent care, ER.

Your plan's pharmacy network is a separate contract from its medical provider network. CVS might be in network for medical (their MinuteClinic urgent care) but out-of-network for pharmacy under the same plan. The pharmacy directory at your plan's member portal is authoritative - third-party pharmacy comparison sites are unreliable.

Within the in-network pharmacies, plans designate some as "preferred" - typically saving $5-30 per fill compared to "standard." Preferred pharmacies are usually large chains under contract: CVS, Walgreens, Walmart, Costco, Kroger, sometimes regional chains. Mail-order pharmacy is almost always preferred - often the lowest-cost option for any maintenance medication.

For a typical retired person taking 3-4 maintenance medications, mail-order saves $200-600 per year vs retail. Setup takes 2-3 weeks for first fill: have your provider send the prescription directly to mail-order, OR mail in your existing 90-day supply with a refill request. Refills are automatic with renewal reminders 2 weeks before run-out.

The ANOC arrives in a thick envelope, usually 30-50 pages. The first 4-6 pages are the "Summary of Changes" - everything you actually need to read. Federal rules require the summary to highlight changes from the current plan year. Page 1 typically shows premium and deductible side-by-side: current year vs next year. Subsequent pages cover OOP max changes, formulary tier changes for specific high-cost drug categories, network changes, and supplemental benefits changes.

The full Evidence of Coverage (EOC) follows the ANOC by mid-October. EOC is the plan's full handbook - hundreds of pages. You don't need to read the whole thing, but the table of contents lets you check specific topics: prior auth requirements, appeal procedures, specific drug formulary placements.

If you don't receive an ANOC by October 5, call your plan and request a replacement. Federal regulation requires plans to provide one on request. Confirm by phone whether your plan still operates next year - some plans get discontinued and you may be auto-enrolled in a different plan from the same insurer with potentially dramatic differences.

QMB is one of four Medicare Savings Programs (MSPs). The four are: QMB (covers everything), SLMB (covers Part B premium only), QI (covers Part B premium, slightly higher income limit), QDWI (for disabled working). QMB has the highest income limits but covers the most. To qualify: income up to 100% FPL ($15,960 single / $21,640 couple, 2026), assets up to $17,600 single / $35,130 couple (2026, includes burial allowance). Many states have higher limits or no asset test.

QMB enrollment is automatic in most states once you qualify for full Medicaid plus Medicare. If you have full Medicaid AND Medicare, you should be QMB. Verify by logging into mymedicare.gov and looking for QMB status, or call your state Medicaid agency. If you're a dual eligible but QMB isn't showing, it's an enrollment error - call your state Medicaid agency to fix.

When a QMB beneficiary receives a bill for a Medicare-covered service, the bill is unlawful. The provider's billing system likely just billed by default - they may not even know you're QMB. Most providers comply once contacted. The bigger issue is when bills go to collections or appear on credit reports - that's when the federal beneficiary protection hotline (1-844-360-7363) becomes essential.

Since the 2024 IRA implementation, the prior partial-LIS tiers were eliminated - everyone eligible for Extra Help now receives the full benefit. Full Extra Help covers everyone with full Medicaid plus Medicare, those with SSI, and those enrolled in a Medicare Savings Program. People with income up to 150% FPL ($23,475 single / $31,725 couple, 2026) and assets within limits can also qualify by application. Beneficiaries with full Medicaid pay $1.60 generic / $4.90 brand. Other LIS recipients pay up to $5.10 generic / $12.65 brand. Both groups have $0 premium for benchmark plans and no deductible.

Extra Help auto-enrolls you in a benchmark Part D plan if you're not already enrolled. Benchmark plans charge $0 premium for full-LIS enrollees. Benchmark plans change yearly - your auto-enrolled plan in 2026 may not be benchmark in 2027. Verify each year. You can switch plans monthly as a dual eligible (Special Election Period for full-LIS), unlike non-LIS enrollees who can only switch during Annual Enrollment.

The auto-enrollment process takes 60-90 days after Medicaid approval. During that lag, you may receive bills at full plan copay rates. These charges should be retroactively adjusted once LIS activates - but you have to follow up. The plan won't automatically refund.

Renewal happens annually based on your enrollment date (not necessarily January). Some states use birthdate; others use anniversary of enrollment. Your most recent Medicaid approval letter shows your specific renewal date. The renewal packet asks for verification of income (Social Security letter, pension statements, bank statements), assets if your state requires (some don't for dual eligibles), and address.

Many states now offer online renewal portals - faster and easier than mail. Set up an account before your first renewal so you're ready. States increasingly do "ex parte" renewals - automatically renewing if your income data verifies through Social Security and tax records - without requiring you to do anything. But you should still verify it happened by checking your account or calling.

If your circumstances changed (income up, assets up, married/widowed, moved), you must report within 10 days under federal rule. Failure to report can result in benefit recovery (state demands repayment of Medicaid paid during ineligible period). Income changes can also shift you from QMB to SLMB/QI - different protections, but still useful.

Priority Groups exist to allocate VA resources when demand exceeds capacity. Higher priority groups get faster access, fewer or no copays, and broader benefits. Lower priority groups still receive care but with copays and sometimes longer waits. Priority Group 8 was closed to new enrollees from 2003-2009 due to capacity constraints; it has since reopened.

Income thresholds for Priority Groups 5-8 are based on the VA's Geographic Means Test (GMT) - adjusted annually and varying by region. The threshold considers your income relative to your local cost of living. For 2026, the basic income threshold (single veteran, no dependents) is approximately $39,849 nationally, with higher thresholds in higher-cost areas. Income includes Social Security, pensions, wages, and most other sources.

Priority Group can change. Increases in service-connected disability rating automatically update your group. Income drops trigger reassessment via VA Form 10-10EZR (Income Worksheet). Becoming Medicaid-eligible automatically triggers Priority Group 5 placement. Aid & Attendance approval triggers Priority Group 4. These updates are not automatic in all cases - you may need to request reassessment.

MyHealtheVet has three account tiers. Basic is limited (mostly information only). Advanced lets you manage prescriptions and appointments. Premium unlocks full features: secure messaging, complete clinical record access, lab results, OpenNotes. Premium requires identity verification - easiest done via Login.gov or ID.me online (about 15 minutes), or in-person at any VA medical center.

Once Premium is activated, you can refill all VA prescriptions online (90-day mail order, free or low-cost). Schedule and reschedule appointments. Send secure messages to your VA care team - usually replied within 1-2 business days, much faster than calling. Read every clinical note immediately after the visit (no waiting for provider release). See lab results as soon as the lab releases them, often before your provider has reviewed.

OpenNotes is the most powerful feature. Every clinical note your VA provider writes is visible to you. This catches documentation errors (wrong diagnosis, wrong medication list), helps you track care over time, and supports informed decisions. Some veterans find this overwhelming initially; most come to value it deeply.

The community care process starts at your VA primary care team. They determine eligibility based on the six categories and submit the referral. You receive an authorization letter with: the community provider's name, specific services authorized, date range of authorization, and your responsibilities (copays per Priority Group, scheduling, follow-up).

Authorizations are highly specific. If your authorization specifies Dr. Smith at ABC Specialists for orthopedic consultation between June 1-30, going to Dr. Jones at XYZ Specialists in July voids the authorization. The community provider may proceed and bill VA, but VA can deny - leaving you with the bill. ALWAYS verify your authorization matches scheduling.

The VA uses regional Community Care Network contractors (TriWest in some regions, Optum in others) to coordinate. After your VA primary care team makes the referral, the contractor schedules with the community provider and handles billing. You receive notifications throughout. The system has improved significantly post-MISSION Act, but errors and delays still happen.

A&A is a TIER of pension, not a separate benefit. It increases the Maximum Annual Pension Rate (MAPR) for veterans who need help with daily activities. The math: VA pays the difference between your countable income (after deducting unreimbursed medical expenses) and the applicable MAPR. A veteran with no dependents needing A&A has a 2026 MAPR of ~$29,093 annual ($2,424/month). If your countable income (after UMEs) is $0, VA pays the full MAPR. If it's $15,000, VA pays $14,093.

Unreimbursed medical expenses are critical to eligibility. UMEs include: assisted living facility costs, in-home aide costs, prescription drug costs, Medicare premiums, Medigap premiums, dental, vision, hearing aids, medical transportation. UMEs are deducted from income BEFORE comparing to MAPR. A veteran with $40,000 income and $25,000 in UMEs has $15,000 countable income - well below MAPR - and qualifies for substantial A&A.

The application uses three forms: VA Form 21-527EZ (pension application, if not already on pension), VA Form 21-2680 (medical evaluation by physician), and various financial documentation (income statements, asset listings, UME records). Processing typically takes 4-8 months. Working with a Veterans Service Officer (free, accredited by VA) significantly reduces error rate and processing time.

DEERS is the Defense Department's enrollment database. It tracks military service members, retirees, and their dependents. TRICARE eligibility flows from DEERS - if you're not in DEERS correctly, you're not eligible for TRICARE benefits regardless of your actual status. SSA notifies DEERS of Medicare enrollment, but the data flow has typical lag of 30-60 days.

When DEERS is current, the TRICARE For Life claims process is fully automatic. Medicare processes the claim first, pays 80% of Part B services. The claim then crosses over to TRICARE, which pays the remaining 20% (or whatever Medicare-approved amount remains). You receive an EOB from Medicare and from TRICARE - both should agree, and you should owe $0 for most Medicare-covered services.

When DEERS lags, the crossover doesn't happen automatically. The provider bills you for the 20% Medicare didn't pay; you have to manually submit to TRICARE for reimbursement. TRICARE eventually pays, but during the lag you may receive bills, calls from collections, or credit reporting if it goes long enough.

Express Scripts is a pharmacy benefit manager (PBM) under contract with DoD to administer TRICARE pharmacy. Beneficiaries can fill prescriptions at three settings: military pharmacies (free for formulary), Express Scripts mail-order (low cost), or retail network pharmacies (higher cost). Network retail pharmacies include CVS, Walgreens, Walmart, Kroger, and many more - but cost is dramatically higher than mail-order for maintenance medications.

Mail-order setup takes 2-3 weeks for first fill. Have your provider send the prescription directly to Express Scripts (electronically via SureScripts or by fax to 1-877-895-1900). Or mail in a written prescription with the patient registration form. Once active, refills are automatic with reminders 2 weeks before run-out.

The mandatory mail-order list (NDAA 2018) targets brand-name maintenance medications where significant savings exist for DoD. After 2 retail fills, the system blocks further retail fills of those specific drugs - you must use mail-order or military pharmacy. The list updates annually; check via TRICARE Pharmacy or Express Scripts.

When you receive Medicare-covered care, the provider bills Medicare. Medicare adjudicates - applies deductible, calculates 80% payment, sends EOB to you and provider. The claim then crosses over electronically to TRICARE via Wisconsin Physicians Service Government Health Administrators (WPS-GHA), the TRICARE For Life contractor. TRICARE adjudicates the secondary claim, pays the remaining cost-share, and sends its own EOB. Total time from service to full settlement: typically 60-90 days.

The crossover sometimes fails. When DEERS isn't current, when the provider doesn't bill Medicare correctly, or when administrative errors happen, the claim doesn't reach TRICARE. The provider then bills you for the 20% Medicare didn't pay. You can either: (1) file a manual claim with TRICARE (DD Form 2642 - TRICARE Claim Form), or (2) ensure DEERS is correct and the provider rebills.

Some services Medicare doesn't cover - for instance, certain dental, vision, hearing, and overseas care. TRICARE has separate rules for these. TFL covers some non-Medicare services under its own benefit structure. The beneficiary handbook explains which services. If Medicare denies a claim, file a TRICARE-only claim using DD Form 2642 and indicate Medicare denial.

FEHB is administered by the Office of Personnel Management. As a retiree with FEHB, you keep coverage in retirement at the same premium structure as active employees (federal contribution continues). FEHB enrollee share rose 12.3% on average for 2026 - the second consecutive year of double-digit increases. Self-only premiums vary widely by plan. FEHB plans vary widely - HMO, PPO, fee-for-service. Each handles Medicare coordination differently.

When you enroll in Part B alongside FEHB, Part B becomes primary for outpatient services. FEHB pays as secondary. Many FEHB plans waive cost-share entirely when Part B is primary, effectively giving you $0 OOP for most services. Some FEHB plans also offer reduced premiums for Medicare-eligible enrollees, partially offsetting the Part B premium.

Without Part B, FEHB pays as primary for everything. Cost-share applies fully. Some FEHB plans charge significantly more in OOP costs without Part B coordination. The math: Part B premium $2,435/year; FEHB OOP without Part B can be $1,500-3,000+ depending on plan. For most retirees with average healthcare needs, Part B nets out near break-even or slightly favorable. For higher-utilization retirees, Part B saves money. For very-high-IRMAA retirees with low utilization, Part B may not pencil.

MRAs are an FEHB plan benefit, not an OPM-wide program. Each plan that offers an MRA defines its own structure: amount, eligible expenses, reimbursement process. Common reimbursable expenses: Part B premium, Medicare deductibles, FEHB copays and coinsurance, sometimes Part D premium and deductible. Some plans require Part A AND Part B; some only require Part A.

Activation often happens automatically when you enroll in Medicare alongside FEHB - the plan recognizes the dual coverage. But submission of receipts is YOUR responsibility. Some plans accept claims monthly; others batch annually. Most have online portals or specific claim forms.

Reimbursement amounts can be substantial. BCBS Federal Employee Program Standard Option 2026 offers up to $800 per individual ($1,600 family) annually in MRA. Aetna HMO plans offer different structures. The biggest mistake is not knowing your plan offers it - many retirees pay Part B premium ($2,435/year) without realizing $800 of it is reimbursable.

Open Season for federal employees and retirees runs simultaneously across all plans. OPM publishes plan brochures and the comparison tool at opm.gov in early November. The comparison tool lets you filter by your situation (active vs retired, with vs without Medicare, family size) and see total annual cost estimates.

Premium changes for 2026 are particularly significant - averaging 12.3% across plans, the largest single-year increase since 2002. Some plans increased less (5-8%); some more (15-20%). Plans with significant Medicare coordination changes for 2026 include several FEHB-MA hybrids. Don't assume your current plan is still the best fit.

Changes made during Open Season take effect January 1. If you stay with your current plan, the new premium and benefits apply automatically. Switch plans by enrolling through OPM Open Season at opm.gov/openseason or via your agency benefits office (still active) or OPM Retirement Services (1-888-767-6738) (retiree).

Renewal happens annually based on your enrollment date. The renewal packet asks for income verification (Social Security, pension statements, pay stubs), assets if your state requires, household composition, and address. Some states use birthdate; others use enrollment anniversary.

Ex parte renewal is increasingly common - states match your data against SSA and tax records, and renew automatically if everything verifies. You may receive a notice indicating renewal happened without action required. But if data doesn't match, you'll receive a packet requiring response.

Income changes during the year trigger reporting requirements (10-day federal rule). Failure to report can lead to benefit recovery (state demands repayment) or termination at next renewal. Major life changes (marriage, divorce, death of spouse, household composition changes, disability rating changes) all require reporting.

Medicaid managed care works like commercial insurance with state Medicaid rules layered on top. You enroll in a specific MCO (chosen at Medicaid enrollment or auto-assigned). All your Medicaid-covered care must go through that MCO's network and processes. Network includes specific providers, hospitals, pharmacies, and facilities under contract with that specific MCO.

Prior authorization applies for many services: imaging, surgery, specialist referrals, DME, some medications. Process is similar to commercial: provider submits request, MCO approves or denies, you have appeal rights. Standard turnaround 14 days; expedited 72 hours.

Plan switching is generally limited. After initial 90-day window, you can switch only once per year (during open enrollment) or for cause (provider leaves network, quality concerns, moving). "For cause" requires documentation; standard reason like "I don't like this plan" is not sufficient.

HCBS waivers operate at the state level under federal authority. Each state designs its own waiver(s) with specific covered services, eligibility rules, and enrollment caps. Some states have multiple waivers serving different populations: aged/disabled adults, individuals with developmental disabilities, technology-dependent children, etc. Your state's Medicaid agency or Area Agency on Aging can identify which waiver fits your situation.

Applying typically requires functional assessment (Level of Care evaluation) AND financial application. The functional assessment determines whether you need nursing home level of care - meaning if not for HCBS, you'd require institutional care. The financial application uses waiver-specific rules; many waivers allow higher income limits than standard Medicaid (some up to 300% SSI federal benefit rate).

Waiting lists are state-specific and waiver-specific. Some states have no waiting list; some have 5+ year waits. Priority is typically given to those at highest risk of institutionalization (currently in nursing home, recently discharged, primary caregiver lost). Apply as soon as you anticipate need - don't wait for crisis.

Medicaid eligibility has multiple categories: ACA expansion (under 65), Aged-Blind-Disabled (65+ or disabled), Long-Term Services and Supports (nursing home, HCBS waiver), Medically Needy (some states allow spend-down), and others. For seniors 65+, ABD Medicaid is the typical pathway - income up to ~100% FPL plus asset limits, often around $2,000 single / $3,000 couple.

Application typically goes through your state Medicaid agency website or by paper form. Some states use Healthcare.gov as initial portal. The application asks for income (Social Security, pensions, wages, all sources), assets (bank accounts, investments, property other than home), household composition, address, citizenship/immigration status. Many states allow online application with electronic verification.

Retroactive coverage is critical for those with recent medical bills. Federal rule allows up to 3 months retroactive - meaning if you apply in March and qualify, coverage can be effective back to December. This can cover hospital bills from a recent emergency, ER visits, or other care during the retroactive period. Some states limit retroactive coverage to 1-2 months under federal demonstration waivers; verify your state's policy.

Hospital charity care policies vary in generosity but follow federal templates. Most policies have multiple tiers: 100% free for income below ~200% FPL, partial discounts above that up to 400% FPL or higher. Some policies extend further (some up to 600% FPL for medically necessary care). Income is typically family income; some hospitals consider total assets, others don't.

Application process: most hospitals have a financial assistance office (sometimes called "financial counseling" or "patient advocate"). You complete an application, provide proof of income and household composition, and they make a determination. Federal rules require notification of decision within reasonable time (typically 30-60 days). If denied or partially approved, you have appeal rights.

Retroactive applications work for past bills, including bills already in collections. Hospitals typically have a lookback period (often 240 days from date of bill, sometimes longer). Applying retroactively can wipe out collections, restore credit damaged by medical debt, and refund payments already made for collections that should have been charity.

Medicare Secondary Payer rules exist to determine which insurance pays first when you have multiple coverages. The 20+ employee threshold reflects historical policy that larger employers should bear primary responsibility, while smaller employers serve as supplements. The rule applies to employers in their entirety - not just your work location. A hospital with 5 employees at your specific location but 500 employees system-wide counts as 500.

If your employer has 20+ employees: enroll in Part A (free for most) but Part B is optional. You can delay Part B without penalty as long as you have current employer coverage. Once you retire or coverage ends, you have an 8-month Special Enrollment Period for Part B.

If your employer has fewer than 20 employees: Medicare is primary, meaning the employer plan won't pay for services Medicare would have covered if you had been enrolled. You should enroll in Part B at 65 - failure to do so means double charges (employer plan denies because Medicare should have been primary, but you don't have Medicare to pick up the share).

When you retire (or lose employer coverage for any reason) at or after 65, your 8-month Part B Special Enrollment Period clock starts immediately. If you elect COBRA, the clock keeps ticking. After 8 months, your SEP closes. If you haven't enrolled in Part B, you'll have to wait until General Enrollment Period (Jan 1 - March 31) and your Part B becomes effective the following July - meaning a 3-15 month gap with no Part B.

Medicare Secondary Payer rules also apply: at 65+, Medicare pays primary; COBRA pays secondary. If you don't have Medicare, COBRA may deny Medicare-eligible services because Medicare would have been primary. Result: you owe what Medicare would have paid (often the larger portion).

Some employer COBRA plans terminate when you become Medicare-eligible. Others continue. Read your specific plan documents. Even if COBRA continues, the cost may exceed Medicare + Medigap premium combined - making COBRA economically inferior.

Multiple SEPs and protections trigger at coverage loss, with different windows. The Part B SEP is 8 months - generous, but the date is calculated from end of employer coverage, not COBRA. The Medigap guaranteed-issue right is 63 days - much shorter, easy to miss. The Part D SEP is also 63 days. All three start at end of qualifying coverage.

Documentation is critical. You need proof of: (1) what coverage you had, (2) when it ended, (3) why it ended (termination, retirement, plan discontinuation, etc.). Acceptable documents: termination letter from employer, COBRA election notice with effective dates, insurance company termination certificate, retirement notice. Save copies of everything.

Medigap guaranteed-issue rights are state-specific in some respects. Federal law protects rights for plans A, B, C, D, F, G, K, and L. Some states have additional protections for other plans or longer windows. Check with your state insurance department or SHIP.