Managing Future Tax Liabilities in Retirement
For many high-earning couples, a substantial 401(k) balance is a double-edged sword. While it represents years of diligent saving, every dollar held in a traditional 401(k) is a deferred tax liability that the IRS will eventually collect. Without a proactive plan, retirees may find themselves forced into higher tax brackets during their later years due to Required Minimum Distributions (RMDs).
Financial experts suggest a strategy known as “bracket filling” to mitigate this risk. By converting traditional 401(k) funds to a Roth account during the years when taxable income is at its lowest, retirees can effectively move money into a tax-free vehicle while paying a lower marginal tax rate.
The Strategic Advantage of the 65-to-73 Window
The period between retiring at age 65 and the onset of RMDs at age 73 offers a unique opportunity. During these years, many individuals see their employment income drop to zero. If they delay claiming Social Security, they may have a window of relatively low taxable income.
By intentionally filling lower tax brackets—such as the 12% bracket—through Roth conversions, a couple can move significant assets out of the traditional 401(k) environment. For a couple with $1.8 million in savings, converting $400,000 over eight years can yield massive long-term benefits. By paying a 12% rate now, they avoid the potential 24% marginal rate they might face later when RMDs, Social Security, and other income sources are combined.
Critical Considerations for Success
Executing this strategy requires careful planning to avoid pitfalls that could erode the tax savings. Key factors include:
- Funding the Tax Bill: Use a separate taxable savings or brokerage account to pay the taxes owed on the conversion. Withholding tax from the conversion amount itself reduces the funds that land in the Roth account, diminishing the long-term compounding benefit.
- Monitoring IRMAA Surcharges: Medicare premiums are subject to the Income-Related Monthly Adjustment Amount (IRMAA). Because IRMAA uses a two-year lookback period, retirees must ensure their Modified Adjusted Gross Income (MAGI) does not inadvertently trigger higher Part B and Part D premiums.
- State Tax Implications: The tax benefit of a conversion can vary significantly depending on where you reside. Some retirees strategically time their conversions to coincide with a move to states with no income tax, such as Florida, Texas, or Tennessee, to maximize their savings.
By shifting $400,000 into a Roth account over eight years, a couple can save approximately $145,000 in lifetime taxes compared to the costs of forced 24% RMDs and associated Medicare surcharges.
Taking Action
Before the tax year closes, it is essential to run a projection of your expected taxable income through age 73. Identify the gap between your projected income and the top of your preferred tax bracket; this gap represents your ideal annual conversion target. Because this strategy interacts with complex variables like Social Security claiming, IRMAA tiers, and state residency, consulting with a fee-only Certified Financial Planner (CFP) or a qualified CPA can help ensure that your specific financial situation is handled correctly.
