The math
Which pocket you spend from is worth more than it sounds.
You spend the same amount either way. You own the same investments either way. The only thing that changes is which account the money comes out of, and on these numbers that decision is worth $157,722 in tax across a retirement.
Three pockets, taxed three ways
Most people arrive at retirement with money in three places, and the difference between them is not what they hold. It is when the government takes its share.
Taxable brokerage. Already taxed going in. Taxed every year on whatever it distributes, whether you wanted the cash or not. Taxed again on the gain when you sell, at preferential rates.
Tax-deferred, the 401(k) or traditional IRA. Never taxed going in or along the way. Every dollar coming out is ordinary income, at your normal graduated rate.
Roth. Taxed going in, then never again. No tax on growth, no tax on withdrawal.
That third column is why the order matters. Spending a dollar from the Roth costs you a dollar. Spending a dollar from the 401(k) costs you a dollar plus the tax, so you have to withdraw more than you spend.
The arithmetic
Worked example
$1,500,000 split as $400,000 taxable, $800,000 tax-deferred and $300,000 Roth. Spending $80,000 a year in real terms, 5% real return, assumed rates of 22% ordinary and 15% long-term, with the taxable account yielding 2% a year that gets taxed as it arrives
- Best order, lifetime tax
- $330,365
- Worst order, lifetime tax
- $488,087
- Difference
- $157,722
Same portfolio, same spending, same returns. The entire gap comes from which account gets drained first.
| Order | Years funded | Lifetime tax | Tax per dollar spent |
|---|---|---|---|
| Tax-deferred first | 29 | $291,492 | 12.6% |
| Taxable, then deferred, then Roth | 30 | $330,365 | 13.8% |
| Proportional, a bit of each | 30 | $346,449 | 14.4% |
| Roth first | 29 | $488,087 | 21.0% |
The last column is the one to read, because the orders do not all fund the same number of years and comparing raw tax totals would flatter whichever ran out soonest. Spending taxable first costs 13.8% of everything you spend. Spending the Roth first costs 21.0%.
Why spending the Roth first feels right and is wrong
It is the most tempting mistake, because Roth money feels free. There is no tax bill when it comes out, so it seems like the efficient thing to use.
But spending it first means you no longer have it later, and later is exactly when you want a pocket you can draw from without generating taxable income. Worse, every dollar of Roth you spend early is a dollar that stops compounding tax-free for the rest of your life. It is the account with the most valuable tax treatment and you have spent it on groceries in year one.
Save the account that is never taxed again for last. It is the only one whose value grows the longer you leave it alone.
The counterintuitive one
Notice that draining the tax-deferred account first produces the lowest total tax bill in the table, at $291,492, and still funds fewer years than spending taxable first. That is worth understanding rather than dismissing.
It pays less tax in total because it stops generating ordinary income sooner. But it also empties the largest account at the start, so less money spends time compounding, and the taxable account sits there throwing off distributions that get taxed every year regardless. Lower total tax is not the same thing as more money reaching you, and optimizing for the smaller tax bill is a common way to end up worse off.
The general rule, and the important exception
The default ordering that falls out of the arithmetic is taxable, then tax-deferred, then Roth. It spends the least tax-advantaged money first and leaves the most advantaged compounding longest.
But treating it as a strict sequence is the refinement most people miss. Draining the taxable account completely and then switching entirely to the 401(k) can push you into a higher bracket in those later years, while wasting the low-bracket space in the earlier ones when your taxable income is small.
The better version is to spend from the taxable account and take just enough from the tax-deferred account each year to fill up the lower brackets, so no cheap bracket space goes unused. That is why the proportional strategy in the table does nearly as well as the strict ordering: blending is closer to right than any pure sequence.
Those early retirement years, after you stop working and before required distributions and Social Security begin, are the cheapest tax years you will ever have. They are the window for exactly this, and for Roth conversions, which is the same idea run in reverse: deliberately realizing income while it is cheap.
What this model leaves out
Required minimum distributions. At a certain age the government forces withdrawals from tax-deferred accounts whether you want them or not. That strengthens the case for drawing some tax-deferred money earlier, because a large untouched 401(k) eventually becomes a large forced withdrawal at whatever rate applies then.
Social Security. Its taxation depends on your other income, so the order you withdraw in affects how much of it is taxed. This is a real interaction and it is not modelled here.
State taxes, and the brackets themselves. We print no bracket figures, for the same reason as the asset location essay: when we last checked, the IRS page publishing them still carried the prior year's numbers and commercial calculators disagreed with each other. Get them from the IRS for your year and nowhere else.
And your future rate is unknown. Everything here assumes flat rates. If yours will be much lower later, deferral is worth more than shown. If rates rise, less.
The general principle survives all of it: spend the money the tax code treats worst, and leave the money it treats best alone for as long as you can. What the arithmetic adds is the size of the prize, and it is larger than the effort required to claim it.
Sources and further reading
The arithmetic is our own and its assumptions are stated above. The account rules it relies on come from the IRS.
- Retirement topics: contributions, Internal Revenue Service, for the account types and current-year limits.
- Topic no. 409, Capital gains and losses, Internal Revenue Service, for the preferential treatment of long-term gains that makes a taxable account cheaper to spend than a 401(k).
- Required minimum distributions FAQs, Internal Revenue Service, for the forced withdrawals this model omits.