Retirement Decumulation Mechanics — Chapter 5: Withdrawal Sequencing — Which Account, In What Order

"In retirement, the largest variable you control is often not your return but the timing of your taxable income."

The Problem This Chapter Solves

The first four chapters covered how much to withdraw. This one covers from where — which does not change your pre-tax assets but can substantially change what you get to spend.

Note the middle row: tax-deferred is not tax-free, it is tax-later. Every dollar owes future income tax at whatever bracket applies when you withdraw — which is the lever you can actually pull.

The Conventional Order and Its Flaw

The textbook sequence: taxable first, then tax-deferred, Roth last. The logic — preserve tax-free growth as long as possible — is sound as far as it goes.

The flaw: leaving the deferred account untouched lets it compound until 73, when RMDs begin and may push you into a far higher bracket than necessary.

Concretely: a retiree with almost no taxable income between 65 and 72 wastes eight years of low-bracket space. By 73 an inflated IRA plus Social Security can force a higher rate and drag along Medicare premium surcharges (IRMAA) and greater taxation of Social Security itself.

The Better Approach: Bracket Filling

Rather than emptying one account before touching the next, deliberately "fill" the lower brackets each year.

1. Estimate this year's spending and existing taxable income (Social Security, pensions, dividends).
2. Determine how much room remains below the next bracket threshold.
3. Withdraw from the deferred account exactly enough to fill the current bracket — even if you do not need the cash.
4. Move what you don't need into a Roth (conversion) or a taxable account.

The effect: you substitute today's known lower rate for the possibly higher rate you would face under forced RMDs.

The window from 65 to 73 is the most valuable tax period of retirement — Social Security may not have started, RMDs have not begun, and spending is often stable. Those eight years do not come back.

How RMDs Constrain Everything

• Currently begin at 73 under SECURE 2.0. This threshold has been changed several times; verify the current year's rule before acting.
• Required amount = prior year-end balance ÷ an IRS life-expectancy factor
• Penalties for missing one are severe
• Roth IRAs are not subject to RMDs during the original owner's lifetime — their key advantage here

The practical meaning: money in a deferred account will eventually be taxed. Your only choice is when — and when determines the rate.

Where Roth Conversions Fit

A conversion moves money from a Traditional IRA to a Roth, paying income tax on the amount this year.

When not to convert: if you must use the converted funds themselves to pay the tax, the benefit shrinks considerably; and if your retirement bracket is clearly below your current one, conversion may not pay at all.

Note how the second row echoes Chapter 2: a bear market is a threat to withdrawals but an opportunity for conversions — the same decline means opposite things for the two actions.

Procedure

1. List balances across all three account types — the starting point for every decision here.
2. Compare after-tax outcomes of different orderings with /tools/tax-smart-withdrawal-planner.
3. In the 65–73 window, size each year's conversion with /tools/roth-conversion-architect.
4. Project future RMDs with /tools/rmd-calculator. If they will push you into a higher bracket, that is the signal to start converting now.
5. Coordinate Social Security timing with /tools/social-security-optimizer — delaying raises the benefit and widens the conversion window simultaneously.
6. Recompute annually. Brackets, rules, and spending all change; this is not a one-time decision.

Relevance to a Retirement Portfolio

A boundary statement is required: the above describes general mechanics, not tax advice for your situation. Brackets, state taxes, IRMAA thresholds, and Social Security taxation interact in complicated ways and the rules change — before an irreversible step like a Roth conversion, confirm the current year's specifics with a tax professional.

One point holds without professional input: withdrawal sequencing is among the few areas of retirement planning offering a certain return.

Investment returns are uncertain; tax saved through sequencing is certain, computable, and independent of market performance. In that respect this chapter shares its logic with Chapter 1 on fees — in a problem full of uncertainty, deal first with the parts you can make certain.

Which is why this sits in Chapter 5 rather than an appendix: for many portfolios the gain available from sequencing exceeds the expected-return difference between a 60% and a 65% equity allocation — and unlike that change, it adds no risk at all.