A brief recap of how each bucket behaves on the way out, so that the trade-offs below have a shared vocabulary. The mechanics of each are covered in chapter “Tax Advantaged Accounts”; the focus here is on the surface they present to the tax code during withdrawal.
Withdrawals are not income. Only the realized gain is taxed at preferential LTCG rates (0%, 15%, or 20%) under IRC §1(h), “Tax on capital gains” if held more than a year, with the 3.8% NIIT under IRC §1411, “Imposition of tax on net investment income” stacked on top above the threshold. The basis itself comes out untaxed. Dividends and interest are taxed annually whether you spend the cash or not. The cleanest source of cash for IRMAA management.
Every dollar withdrawn is ordinary income, indistinguishable from wages for federal-bracket purposes. Subject to RMDs under IRC §401(a)(9), “Required distributions” starting at 73 (born 1951–1959) or 75 (born 1960 or later), per SECURE 2.0. The largest single lever you can move during the conversion window.
Qualified withdrawals are not income at all—they do not appear on the Form 1040, they do not raise AGI, they do not feed IRMAA, they do not phase in Social Security taxation. The HSA under IRC §223, “Health savings accounts” adds the requirement of qualified medical use (or post-65 ordinary-income use); the Roth under IRC §408A, “Roth IRAs” is unconditional after age 59½ and the five-year clock (section “Individual Retirement Arrangements (IRAs)”). For decumulation purposes, treat these balances as the most expensive to refill and the cheapest to drain—and as the one balance whose withdrawal mix you control without touching the tax return.
For readers who keep active business interests in retirement—consulting, board fees, royalties, a closely held operating company—the C-corp functions as a fourth bucket the textbook three-bucket model ignores. The TCJA’s flat 21% corporate rate has been permanent under IRC §11(b), “Tax imposed on corporations” since 2017, and OBBBA’s permanent IRC §199A, “Qualified business income” turned the pass-through-vs-C-corp choice into a real comparison rather than a permanent bet. The relevance to decumulation: revenue earned by a C-corp pays 21% inside the entity and generates exactly $0 of personal AGI until you choose to pay yourself a salary or a dividend. $250,000 of consulting income on a sole-proprietorship Schedule C lands on your 1040 in full, spikes AGI, blows through IRMAA tiers, and drags 85% of your Social Security through the torpedo. The same revenue billed through a C-corp can sit at 21% inside the wrapper while you pay yourself the precise dollar amount that leaves your personal MAGI $1 below the cliff you have chosen. The trade-offs—reasonable-comp requirements if you are also an employee, accumulated-earnings tax exposure on undistributed earnings without business purpose, double taxation on dividends eventually paid out, the cost of running a second tax return—are real and treated in chapter “The Business Owner’s Tax Architecture”. As a decumulation tool, the C-corp is the only legal entity that lets you decouple the timing of earning income from the timing of recognizing it.
The asymmetry between pre-tax and Roth, on the way out, is total: $100,000 of pre-tax withdrawal can cost you 32% federal + state + IRMAA + lost ACA subsidy, while $100,000 of Roth withdrawal costs you nothing and is invisible. The instinct to “save the Roth for last” optimizes the wrong thing.