Tax Planning for Retirement: RMDs, Roth Conversions, and Minimizing Your Bill

Why Retirement Tax Planning Is Different

During your working years, tax planning primarily revolves around deferring income and maximizing deductions. In retirement, the equation flips: you transition from accumulation to distribution, drawing down assets accumulated in tax-advantaged accounts, and the tax decisions you make each year can have compounding effects on your lifetime wealth and what you leave to heirs.

Retirees often face multiple income streams — Social Security benefits, required minimum distributions from traditional IRAs and 401(k)s, pension payments, investment income from taxable accounts, and potentially part-time earned income — each with different tax characteristics and interactions. Managing these streams strategically, rather than simply drawing from accounts as needed, can mean the difference of hundreds of thousands of dollars in taxes over a 20 to 30-year retirement.

The most important insight in retirement tax planning is that a low-income year is a planning opportunity, not just a low-tax year. The years between retirement and the onset of required minimum distributions — often ages 60 to 72 or 73 — represent a window to take strategic actions (like Roth conversions) while income and tax rates are relatively low, setting up a more tax-efficient financial picture for the decades ahead.

Understanding Required Minimum Distributions

Required minimum distributions (RMDs) are mandatory annual withdrawals from traditional IRAs, 401(k)s, 403(b)s, and most other tax-deferred retirement accounts. The SECURE 2.0 Act raised the RMD starting age to 73 for individuals who turn 72 after December 31, 2022, with a further increase to 75 scheduled for 2033. The purpose of RMDs is to ensure that the tax-deferred balances accumulated over a lifetime of saving eventually flow through the tax system.

The annual RMD amount is calculated by dividing your prior December 31 account balance by your life expectancy factor from the IRS Uniform Lifetime Table. As you age and your account balance grows, RMDs can become very large — and they are all taxed as ordinary income in the year taken. A retiree with $2 million in IRAs at age 75 might face an annual RMD of $85,000 to $100,000, which could push them into a higher tax bracket, increase the taxable portion of Social Security benefits, and trigger higher Medicare premiums.

Failure to take your full RMD by the December 31 deadline (April 1 for your first RMD) results in a penalty of 25% of the shortfall — reduced to 10% if corrected promptly. Roth IRAs owned by the original account holder are not subject to RMDs during the owner's lifetime, which is one of their most attractive features for retirement planning.

Roth Conversions: The Core of Retirement Tax Strategy

A Roth conversion involves moving money from a traditional IRA (or other pre-tax retirement account) to a Roth IRA. The converted amount is added to your taxable income in the year of conversion and taxed at ordinary rates. After that, the money grows tax-free in the Roth account and future withdrawals are completely tax-free.

The strategic rationale for Roth conversions in retirement is to take advantage of lower tax rates during the gap years before RMDs begin — or in years with temporarily low income — to reduce future RMD burdens. By converting pre-tax balances to Roth, you reduce the size of accounts subject to RMDs, potentially keeping you in lower tax brackets in your 70s and 80s when RMDs would otherwise force large taxable distributions.

The optimal conversion amount each year typically fills your current tax bracket to its upper boundary without pushing into the next. For example, if your Social Security and other income puts you at $50,000 in taxable income and you are in the 22% bracket, you might convert enough to bring taxable income up to the top of the 22% bracket ($89,075 for single filers in 2025), but not into the 24% bracket. Partial conversions across multiple years, rather than a single large conversion, tend to be more tax-efficient.

Social Security Taxation and the Combined Income Trap

Up to 85% of Social Security benefits can be subject to federal income tax, depending on your "combined income" — adjusted gross income plus non-taxable interest plus half of your Social Security benefit. If combined income is between $25,000 and $34,000 for single filers (or $32,000 to $44,000 for married filing jointly), up to 50% of benefits are taxable. Above those thresholds, up to 85% is taxable.

This creates what some call the Social Security "tax torpedo" — a zone of income where each additional dollar of income generates $1.85 in taxable income (your income plus 85 cents of newly taxable Social Security). In this zone, your effective marginal tax rate is significantly higher than your statutory bracket rate. For example, someone in the 22% bracket who is in the Social Security phase-in range effectively pays 22% × 1.85 = 40.7% on marginal income — higher than many taxpayers pay in top brackets.

Roth conversions done before Social Security begins can reduce future combined income, preventing this tax torpedo from firing in later years. Delaying Social Security until age 70 to receive the maximum benefit can actually be tax-advantaged in this context: a larger Social Security payment may be partially offset by lower RMD income if pre-tax accounts have been reduced through earlier Roth conversions.

Medicare Premiums and the IRMAA Surcharge

Medicare Parts B and D premiums are not flat rates — they increase significantly for higher-income beneficiaries through the Income-Related Monthly Adjustment Amount (IRMAA). IRMAA surcharges are based on your Modified Adjusted Gross Income (MAGI) from two years prior, so 2025 Medicare premiums are based on 2023 income. If your 2023 MAGI exceeded $103,000 as a single filer or $206,000 as a married couple, you pay significantly higher premiums.

In 2025, the base Medicare Part B premium was $185 per month, but the highest IRMAA tier pushed it to $628.90 per month — more than three times the base amount. For a married couple at the highest tier, the combined premium surcharge exceeds $10,000 per year. This creates strong incentives to manage MAGI carefully in retirement, particularly in years two prior to Medicare enrollment.

Large Roth conversions, IRA withdrawals, capital gain realizations, or other income events that push MAGI above IRMAA thresholds can trigger premium surcharges for two future years. Smoothing income across years — taking smaller conversions or realizing gains gradually rather than in large lumps — helps stay below IRMAA thresholds while still accomplishing tax-planning goals. An IRMAA appeal process also exists for life-changing events (retirement, divorce, death of spouse) that caused income to be temporarily elevated.

Withdrawal Sequencing: Which Accounts to Tap First

The order in which you draw from different account types significantly affects your lifetime tax bill. The conventional wisdom — draw taxable accounts first, then tax-deferred, then Roth — is a reasonable starting point but is not always optimal. The right sequencing depends on your specific account balances, tax brackets, Social Security timing, state taxes, and estate planning goals.

A more sophisticated approach considers tax diversification: maintaining balances in taxable, tax-deferred, and Roth accounts simultaneously and drawing from the source that keeps your marginal tax rate lowest in each given year. In a year with unexpectedly low income, you might draw more from a traditional IRA or execute a Roth conversion. In a high-income year, you might favor Roth withdrawals that add nothing to taxable income. This flexible approach optimizes each year's tax position rather than mechanically depleting one account type before touching another.

For retirees with taxable investment accounts, asset location also matters: holding tax-efficient assets (index funds, growth stocks held for the long term) in taxable accounts and less tax-efficient assets (bonds, REITs, actively managed funds) in tax-deferred accounts maximizes after-tax returns from the overall portfolio. The interplay between withdrawal sequencing and asset location adds another dimension to retirement tax planning that benefits from comprehensive annual review with a qualified financial advisor or tax professional.