The $1.5 Million 401(k) Tax Trap: How Bracket Smoothing Saves Retirees From 40% Effective Rates

2 hours ago 3

Marc Guberti

Sun, June 14, 2026 astatine 10:24 AM CDT 5 min read

Quick Read

Retirees with ample accepted 401(k)s tin look effectual marginal rates adjacent 40% erstwhile RMDs, Social Security taxation, and Medicare IRMAA surcharges stack simultaneously astatine property 73.
Married couples tin person astir $133,000 annually from pretax 401(k) to Roth astatine a 12% rate, paying astir 9% effectual taxation earlier hitting the 22% bracket.
Always wage Roth conversion taxes from a taxable brokerage account, due to the fact that withholding from the converted equilibrium shrinks the Roth and tin trigger a 10% punishment if you are nether property 59½.
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A mates retires astatine 62 with $1.5 cardinal divided crossed 2 accepted 401(k) plans, nary pension, and Social Security connected clasp until 70. They consciousness financially set. Eleven years later, required minimum distributions propulsion them into the 22% national bracket, resistance 85% of their Social Security payment into taxable income, and trigger Medicare IRMAA surcharges that travel them the remainder of their lives. The strategy that prevents each of that is called bracket smoothing, and the model to usage it closes the time the archetypal RMD hits.

Two elder individuals are seated astatine a table, focused connected fiscal documents and a metallic laptop. An African American antheral with a grey beard and glasses holds a paper, pointing astatine it. Next to him, a Caucasian pistillate with abbreviated grey hairsbreadth successful a bluish garment holds different papers and points astatine thing connected the table. A achromatic textured java mug is successful the foreground.

The 12% Bracket Is the Whole Game

For a joined mates filing jointly successful 2026, the 12% national bracket ends astatine $100,800 of taxable income. The modular deduction is $32,200. Stack them, and a retired mates with nary different income tin propulsion astir $133,000 retired of a pretax 401(k) each twelvemonth earlier a azygous dollar gets taxed astatine 22%.

Single filers person a tighter window. The 12% bracket ends astatine $50,400, the modular deduction is $16,100, and the ceiling lands adjacent $66,500 of gross withdrawals earlier the 22% furniture kicks in.

That ceiling is the full thesis. Every dollar moved from pretax into Roth astatine 12% contiguous is simply a dollar that volition not beryllium forced retired astatine 22% oregon 24% later, erstwhile RMDs, Social Security taxation, and Medicare premiums stack connected apical of each other.

What $1.5 Million Looks Like Under Each Path

Take the mates above. Between 62 and 70 they person an eight-year model with nary earned income and nary Social Security check. If they person $100,000 a twelvemonth from accepted 401(k) to Roth, taxable income lands adjacent $67,800 aft the modular deduction. Federal taxation connected that conversion runs astir astir $7,600. Filling the bracket each the mode to the ceiling costs $11,600, oregon astir 9% effective.

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