Tax-Torpedo & IRMAA Calculator
Two effects hit retirees in a specific income band: the Social Security tax torpedo (each extra dollar of ordinary income pulls more SS into taxation) and the IRMAA cliffs (Medicare premium surcharges that aren’t phase-ins — they’re cliffs). This tool quantifies your effective marginal rate and your safe Roth-conversion ceiling.
How this works: Models IRC §86 SS taxability (50%/85% phases) and 2026 IRMAA Part B+D surcharge thresholds. Effective marginal rate is your nominal rate × 1.0 / 1.5 / 1.85 depending on whether the next dollar pulls 0/50/85¢ of additional SS into taxable income. State tax, alternative minimum tax, and actual federal bracket math (we use a single marginal rate as a simplification) are not modeled.
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