The Roth conversion ladder and the 5-year rule

The mechanic in one paragraph

Money in a traditional IRA or 401(k) taken before age 59½ is generally taxed as ordinary income plus a 10% additional tax under IRC §72(t). A Roth conversion ladder works around the penalty, not the tax: each year you convert one "rung" from the traditional account to a Roth IRA, pay ordinary income tax on the converted amount that year, and wait. Once a conversion has seasoned for five taxable years, that converted principal can come out of the Roth tax-free and penalty-free at any age. Repeat annually and, from year six onward, a rung unlocks every year — a conveyor belt of accessible money that started life behind the 59½ wall. The tax is prepaid, not avoided; what the ladder buys is access, at ordinary rates you choose the timing of.

Two different 5-year rules — do not conflate them

The phrase "Roth 5-year rule" covers two separate clocks, and mixing them up produces expensive mistakes:

• The per-conversion seasoning rule (IRC §408A(d)(3)(F); Treas. Reg. §1.408A-6, Q&A-5). Each conversion carries its own 5-taxable-year period. Withdraw converted principal inside that period, before 59½, and the 10% additional tax applies to the taxable-at-conversion amount — even though no income tax is due on it a second time. This is the ladder's clock.
• The qualified-distribution rule (IRC §408A(d)(2)(B)). A separate, account-level 5-year clock — starting with the first year you ever funded any Roth IRA — that, together with reaching 59½ (or death, disability, first home), makes earnings come out tax-free. The ladder does not touch this rule, because a ladder never plans to withdraw earnings early.

The regulation's counting convention is the detail that matters for scheduling: the 5-taxable-year period "begins on the first day of the individual's taxable year in which the conversion contribution was made" and ends on the last day of the fifth year. The clock is backdated to January 1 of the conversion year regardless of when in the year you convert. A conversion executed December 31, 2026 is treated as seasoning since January 1, 2026 and unlocks January 1, 2031 — roughly 4 years and a day of real waiting. A January 2027 conversion waits nearly the full five. Late-year conversions also give you the whole year's income picture before you commit to the rung size, which matters below.

Why seasoned principal comes out first: the ordering rules

Roth IRA distributions follow fixed ordering rules (IRC §408A(d)(4); Treas. Reg. §1.408A-6, Q&A-8) — you cannot choose which dollars you are withdrawing, but the mandatory order is exactly the one a ladder wants:

1. Regular contribution basis first — always tax- and penalty-free, at any age, with no seasoning. If you have years of direct Roth contributions, that basis is bridge fuel available on day one.
2. Conversions next, first-in-first-out, oldest rung first — tax-free always; penalty-free once that rung's five taxable years have run.
3. Earnings last — these stay behind the 59½ wall (plus the qualified-distribution rule) and the ladder leaves them there.

One more scheduling fact: since 2018, a conversion cannot be recharacterized (undone). The year you convert, that income is on your return for good — which is why the rung-size constraints in the next sections deserve more attention than the seasoning arithmetic.

The ladder timeline, concretely

Illustrative schedule for someone who stops work at the end of 2026 and converts a rung each year starting 2027:

Conversion made in	5 taxable years counted	Penalty-free from	Real wait if converted in December
2027	2027–2031	Jan 1, 2032	~4 yr 1 day
2028	2028–2032	Jan 1, 2033	~4 yr 1 day
2029	2029–2033	Jan 1, 2034	~4 yr 1 day
2030	2030–2034	Jan 1, 2035	~4 yr 1 day
2031	2031–2035	Jan 1, 2036	~4 yr 1 day

Nothing converted in 2027 is usable before 2032. That five-year hole — the cold start — is the actual design problem, and it is the part most ladder calculators wave away by assuming a bridge account that grows at a smooth flat rate. The roth conversion ladder calculator models the seasoning queue and the bridge together, runs the bridge through historical return paths rather than a flat assumption, and reports a pass/fail gate with a range — because a bridge that survives the median path can still fail the bad ones.

Bridge design: what pays for years one through five

The bridge stack, roughly in the order most plans draw it:

• Taxable brokerage. Usually the main span. Note the useful interaction: for 2026, long-term gains stack on top of ordinary taxable income and are taxed at 0% up to $49,450 of taxable income (single; $98,900 MFJ, per Rev. Proc. 2025-32, asOf 2025-10) — but every dollar of conversion is ordinary income that fills that bracket space first. Rung size and 0%-gain harvesting compete for the same room; you are choosing a split, not getting both in full.
• Cash and equivalents. Lower expected return, but immune to the sequence problem below.
• Existing Roth contribution basis. Accessible any time under the ordering rules; a useful shock absorber in a bad market year.
• A §72(t) SEPP — the parallel lane compared below, usable alongside a ladder by splitting IRAs.

Naive sizing is spending × five years — $40,000 a year of spending implies a $200,000 bridge — plus the conversion taxes if you intend to pay those from the bridge too (you should plan to; see the trap below). But naive sizing assumes the bridge holds its value while being drawn down. A bridge held in equities and started into a bad sequence gets hit twice: the S&P 500 total return was −9.0%, −11.9%, and −22.0% in 2000–2002, and −36.6% in 2008 (Damodaran, NYU Stern, 1928–2025 series, asOf 2026-01). Selling into those markets to fund spending converts temporary drawdown into permanent depletion — the same sequence-of-returns mechanism that governs any withdrawal plan, compressed into a five-year window with no flexibility on the far end, because the far end is the date your first rung unlocks. A cold-start bridge that would have lasted five years at a flat 6% projection can fail in year three or four on a 2000- or 2008-style path. This is why the calculator's output is a pass/fail across historical start years and a p5/median/p95 band, not a single terminal number.

Sizing the rung: the bracket you expect, the cliff you forget

Each rung is ordinary income, so the classic move is to fill the low brackets. For 2026 (Rev. Proc. 2025-32, asOf 2025-10), a single filer with no other income could convert $66,500 gross — the $16,100 standard deduction plus the $50,400 top of the 12% bracket — for about $5,800 of federal tax, an effective rate near 8.7% on money that was deducted at higher rates while working. That is the textbook version, and for many early retirees it is not the binding constraint.

The binding constraint in 2026 is often health insurance. The enhanced premium tax credit expired December 31, 2025, and the original §36B schedule is back for coverage year 2026 — including the 400%-of-FPL eligibility cliff (CRS R48290; KFF). ACA MAGI is essentially AGI with a few add-backs: the standard deduction does not shelter it, and every dollar of conversion counts. For a single-person household in the 48 contiguous states, 400% of the applicable FPL is 4 × $15,650 = $62,600 (HHS ASPE 2025 guidelines, applied to coverage year 2026; asOf 2025-01). Notice that this sits below the $66,500 that the 12% bracket alone would suggest — the cliff binds before the bracket does.

And it is a cliff, not a slope. At 399% FPL you pay at most 9.96% of MAGI toward the benchmark plan (Rev. Proc. 2025-25, asOf 2025-07); at 401% the entire credit is gone. On 2026 national-average benchmark premiums (KFF, asOf 2026-01), the credit forfeited by crossing the line is illustratively ~$1,300 a year for a single 40-year-old, ~$11,400 for a single 64-year-old, and roughly $27,000 for a 64-year-old couple — lost on the marginal dollar of conversion. Spread over the last $1,000 of a rung, that is an effective marginal rate that can exceed 1,000%. A rung plan that ignores the cliff is not slightly wrong; it is wrong by the price of a year of health insurance.

The other lane: a §72(t) SEPP

A ladder is not the only penalty-free path to pre-59½ IRA money. Under §72(t)(2)(A)(iv), a series of substantially equal periodic payments (SEPP) escapes the 10% additional tax from the first payment — no five-year cold start at all. The current rules are in IRS Notice 2022-6 (asOf 2022-01): three permitted methods (RMD, fixed amortization, fixed annuitization), with the amortization and annuitization methods allowed to use any interest rate up to the greater of 5% or 120% of the federal mid-term rate for one of the two months before payments begin.

	Roth conversion ladder	§72(t) SEPP
First usable dollar	~4–5 years after the first conversion	Immediately
Amount per year	You choose each rung (within bracket/cliff constraints)	Formula-set; nearly frozen once started (one switch to the RMD method allowed)
Commitment	None — skip or resize any year's rung	Must run the longer of 5 years or until 59½; a 45-year-old is locked for ~14½ years
If you break it	A short rung just means a thinner year later	The 10% tax applies retroactively to every payment, plus interest (§72(t)(4))
Tax character	Ordinary income in the conversion year, at times you pick	Ordinary income every year, on the formula's schedule
ACA interaction	Rung size is adjustable around the cliff	Payment is MAGI every year whether convenient or not

Scale, illustratively: for a 45-year-old with a $500,000 IRA, the Single Life Table divisor is 41.0 (Treas. Reg. §1.401(a)(9)-9(b), effective 2022), so the RMD method pays about $12,200 in year one, while fixed amortization at the 5% floor rate pays about $28,900 per year — a low/high band of roughly $12,000–$29,000, before any month's 120%-of-mid-term rate exceeds the floor and lifts the ceiling. That band is the SEPP's defining trait in both directions: meaningful income with no seasoning wait, purchased with near-total rigidity for fourteen-plus years. Many plans use both lanes — a SEPP carved out of a split-off IRA to cover a floor of spending, with a ladder running beside it for the flexible layer. The calculator shows the SEPP band as a parallel lane next to the ladder's unlock schedule so the trade is visible instead of asserted.

Run it on your own numbers

Rules of thumb end where your actual balances, spending, and start year begin. The Roth conversion ladder calculator builds the per-rung seasoning queue, runs your bridge through historical sequences with a pass/fail gate, prices withholding honestly, marks where the 2026 ACA cliff caps a rung, and draws the §72(t) band beside it — all outputs as ranges with sources and as-of dates. Pair it with the safe withdrawal rate calculator for what happens after 59½, and the barista-FIRE calculator if part-time income is part of the MAGI picture.

Limitations worth keeping in view

Everything here is federal only — state income tax on conversions varies and can change the rung arithmetic materially. The pro-rata rule (IRC §408(d)(2)) applies if your traditional IRAs hold nondeductible basis; conversions from mixed IRAs are partly nontaxable and the seasoning analysis tracks the taxable-at-conversion portion. Employer-plan rules differ from IRA rules (some 401(k)s allow penalty-free access at 55 after separation — the "rule of 55" — which can shorten or replace a bridge). IRMAA is not modeled and matters near Medicare age. The ACA figures are projections contingent on legislation, as flagged above. And the historical bridge paths are one country's market record, not a forecast: the method, data, and every assumption are on the methodology page, and every output is an estimate presented as a range because that is the only honest shape for it.