Retirement Planning Glossary

Plain-language definitions with primary sources. Every numerical claim links to IRS.gov, SSA.gov, or peer-reviewed research.

Tax & Withdrawal Rules

IRMAA (Income-Related Monthly Adjustment Amount)

A Medicare premium surcharge added to Part B and Part D costs for beneficiaries with income above specific thresholds. Cliff-style thresholds mean a $1 of extra income can trigger $2,000-$8,000 in annual Medicare surcharges — making IRMAA a critical variable in Roth conversion planning.

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Roth Conversion Ladder

A multi-year strategy of converting Traditional IRA or 401(k) funds to Roth during low-income years (typically between early retirement and Social Security/RMD start), reducing lifetime taxes and enabling penalty-free Roth withdrawals after a 5-year waiting period.

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Modelling Concepts

Monte Carlo Simulation

A statistical method that runs thousands of randomised market return sequences to estimate the probability that a retirement plan survives to a target age. More reliable than linear-projection calculators that assume a fixed annual return.

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Safe Withdrawal Rate (SWR)

The maximum annual withdrawal rate from a retirement portfolio that historical data suggests will not deplete the portfolio over a given retirement horizon. Commonly set at 4% (the '4% rule'), though actual safe rate depends on horizon length, asset allocation, and success-probability target.

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Sequence-of-Returns Risk

The risk that a series of negative market returns early in retirement permanently impairs a portfolio — even if long-term average returns are identical to a luckier retiree's. The order of returns matters; a fixed-return calculator cannot model this risk.

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