{
  "meta": {
    "seed": 20260710,
    "engine": "irmaa-roth-1.1.0",
    "part_b_base": 202.9,
    "lookback_years": 2
  },
  "headline": {
    "tier1_first_dollar_per_person": 1148.4,
    "tier1_first_dollar_per_couple": 2296.8,
    "worst_small_crossing": {
      "status": "mfj",
      "start_magi": 265000,
      "conversion": 10000,
      "surcharge_one_year": 3472.8,
      "surcharge_pct_of_conversion": 0.3473,
      "extra_effective_rate_now": 0.315
    }
  },
  "finding": "Crossing the first 2026 IRMAA tier costs a single filer $1,148.40/yr (Part B + Part D) and an MFJ couple $2,296.80/yr \u2014 a one-time cliff triggered two years after the income year. Because the surcharge is a fixed dollar amount, a small conversion that just clips a new tier is punished far harder per dollar than a large one: the cheapest place to stop a conversion is the top of your current tier, and crossing a boundary is worth it only when the rate you would pay later clears the break-even rate (rate now plus the amortized cliff)."
}