Insight IRMAA tier edge premium cliff

Extra annual Medicare premiums (Part B plus Part D surcharge, all Medicare-age people) that a MAGI just over an IRMAA threshold triggers two years later, versus MAGI one dollar under the threshold.

Field: IRMAA tier-edge premium cliff Unit: US dollars Basis: nominal dollars Computed by: Engine Status: Complete chain

Appears in: insights (irmaa-tier-edge card impact text "save roughly $X of Medicare premiums" and the rough estate delta)

Calculation records

• IRMAA tier-edge household Medicare premium cliff Model record, justified by derivation

  Purpose: The extra annual Medicare premium a MAGI just over an IRMAA threshold triggers two years later, versus MAGI one dollar under it.

  Statement: For a selected IRMAA edge with n Medicare enrollees in the charge year (lookback MAGI year + 2): cliff = n × ((Part B + Part D surcharge)_just-above − (Part B + Part D surcharge)_one-dollar-below), using the healthcare-premium scale for the charge year. Units: nominal dollars per year. Rounding: none; the card floors a negative difference at 0.

  Formula: cliff = n (P_above − P_below); P = partBAnnual + partDSurchargeAnnual

  • n: Medicare enrollees (alive, age 65+) in the charge year (unit: people) (domain: integer n >= 1)
  • P_above: Per-person annual Part B + Part D premium just above the MAGI threshold, already resolved (unit: usd/year) (domain: finite)
  • P_below: Per-person annual Part B + Part D premium one dollar below the threshold, already resolved (unit: usd/year) (domain: finite)

  Timing: charge year = MAGI year + 2 (the statutory lookback)

  Rounding: a negative (P_above − P_below) is floored at 0 before multiplying by n; the card publishes whole-dollar strings (formatWholeUsd, Math.round) and the evidence asserts the published figure

  Limits:

  • A rough avoidance signal, not a claim that reducing current-year income changes a premium already charged
  • The worksheet supplies the already-resolved per-person premiums; the evidence passes those through rather than recomputing medicareAnnualPremiumPerPerson
  • The Insight only fires when MAGI is at most $5,000 over the next threshold; that proximity window is a screen, not part of the cliff identity

  Provenance: derived by codex, implemented by grok.

  Independent review: cursor

  Gates (6 of 6 pass): fixture registers a test: pass; pins resolve: pass; families exist: pass; worksheet exists: pass; mutation receipt exists: pass; provenance independent: pass

  Worksheet: insight-irmaa-tier-edge-premium-cliff.md Mutation receipt: insight-irmaa-tier-edge-premium-cliff.mutation.md

  Evidence tests: irmaaTierEdge.evidence.test.ts

  Implemented in: irmaaTierEdge.ts

  Is the number of: insight-irmaa-tier-edge-premium-cliff

  Feeds: insight-impact-ending-after-tax-estate-delta

Engine source: engine/src/insights/detectors/irmaaTierEdge.ts (irmaaTierEdge.screen (annualPremiumCliff))