Rule 1: Individual insurance is not creditable for Medicare deferral
The "20-employee" rule that lets some employees defer Part B without penalty doesn't apply to you. Individual market plans (ACA marketplace, short-term, off-marketplace) are NOT considered creditable employer coverage for Medicare purposes. The penalty clock starts at 65 regardless of whether you have other coverage.
Rule 2: Your ACA premium tax credits disappear at 65
If you're on an ACA marketplace plan with Premium Tax Credits (PTC), you become Medicare-eligible the month you turn 65. Once eligible for Medicare Part A (premium-free or otherwise), you're no longer eligible for ACA PTCs. Marketplace plans without subsidies are typically $1,500-$3,000+/month for someone 65 — far more than Medicare's standard $202.90/mo Part B premium plus a Plan G + Part D combination.
Rule 3: Most insurers won't sell individual plans to 65+
Off-marketplace individual health insurance for people 65 and older is rare. Most major insurers don't write new individual policies for Medicare-eligible adults — they assume you'll use Medicare. The few that do (specialty short-term plans, major medical) are typically expensive and have coverage gaps.
Rule 4: Part A is usually free anyway
If you've worked 40+ quarters paying Medicare taxes (10+ years), Part A has no premium. There's almost no financial reason to skip Part A — the only common reason is to keep contributing to an HSA, which requires you to delay enrollment in any Medicare program. That's a specific, narrow case.
Rule 5: Part B is where the real decision is
The standard 2026 Part B premium is $202.90/month — $2,435/year before IRMAA. If you're self-employed with significant net income, you can also deduct that premium above-the-line on Schedule 1 of Form 1040 (see our employer-coverage guide). At a 22% federal marginal rate plus state, the after-tax cost of Part B is closer to $1,800/year — for primary insurance from the federal government with no underwriting.
The math: Part B + Plan G + Part D for a typical self-employed retiree ends up costing $4,000-$5,500/year, with the self-employed premium deduction recovering ~$1,000-$1,500. That's net of taxes, total annual healthcare cost, including catastrophic protection that individual plans don't provide. Almost no individual market option for 65+ comes close.