Convert Before You Claim SS at 70: the 62-70 Bridge

The decision: Margaret and Tom, retiring at 65 in Georgia

Margaret (65) and Tom (66) retired this year in Atlanta. They file married filing jointly. Between them they hold $1.4 million in traditional IRAs and 401(k)s, plus $350,000 in a taxable brokerage account and $80,000 in cash. They have decided to delay Social Security until 70 to lock in the maximum benefit — an 8% delayed retirement credit for each year past their full retirement age of 67 (SSA), turning a $3,000/month FRA benefit into roughly $3,720/month at 70 for the higher earner.

That delay decision quietly hands them the most valuable tax window of their lives. From 65 to 69 they have no Social Security income and no required minimum distributions (their first RMD is at 73). Their only taxable income is about $14,000 of dividends and interest from the brokerage account. They live on cash and brokerage withdrawals. The question on the table: how much should they convert from their traditional IRAs to Roth IRAs during these five bridge years?

The answer, with the math below: $100,000 per year, every year from 65 through 69 — $500,000 total — almost all of it taxed at 22%. If they convert nothing and wait, that same $500,000 (grown to more) comes out later as RMDs taxed at 24% or higher, while 85% of their Social Security is also taxable. The bridge years are the arbitrage.

Why the 62–70 gap is a tax window, not just a waiting period

Three things normally pile income into a retiree’s tax return at the same time: Social Security benefits, required minimum distributions, and any wages or pension. When you delay Social Security to 70, you deliberately remove the first of these for several years. RMDs do not start until 73 for anyone born 1951–1959, or 75 for those born 1960 or later (SECURE 2.0 Act §107). If you have stopped working, your wage income is gone too.

That leaves a stretch — often five to eight years — where your taxable income can be near zero unless you choose to create some. The 10%, 12%, and 22% brackets sit empty. A Roth conversion is voluntary income: you decide how much traditional IRA money to move to a Roth and pay tax on it now, at today’s low bracket, so it grows and comes out tax-free forever after — and so it never becomes an RMD.

For 2026, the married-filing-jointly brackets that matter here:

Source: IRS Rev. Proc. 2025-32 (2026 inflation adjustments). The 22% bracket alone holds $109,750 of width for a married couple. Add the $31,500 MFJ standard deduction (plus the $1,250 age-65 add-on per spouse) and the room is even larger before you cross into 24%.

The math: converting $100,000 a year, 65 through 69

Here is what a single bridge year looks like for Margaret and Tom. They convert $100,000 from Tom’s traditional IRA. Their only other income is $14,000 of dividends and interest.

Notice the result: with the dividends and the doubled-up standard deduction soaking up the bottom, the entire $100,000 conversion lands in the 12% bracket. Margaret and Tom could push harder — the top of the 22% bracket is $206,700 of taxable income, so after their $34,000 of deductions and $14,000 of dividends they could convert roughly $227,000 in a single year before crossing into 24% — but they cap at $100,000 deliberately to stay under the Medicare IRMAA threshold (more on that below) and to spread the conversions evenly across five years rather than spiking one.

Across 65–69 that is $500,000 converted, the bulk taxed at 12–22%. Georgia’s flat 5.39% income tax (dor.georgia.gov) adds a state layer, but the federal saving dwarfs it. Compare the alternative.

What it costs to skip the bridge

Suppose they convert nothing. The $1.4 million keeps compounding tax-deferred. At 73, RMDs begin. The first-year divisor under the IRS Uniform Lifetime Table (Pub. 590-B, Table III) is 26.5 at age 73 — about 3.77% of the prior-year-end balance. On a balance that has grown to, say, $1.8 million, that is a $68,000 forced withdrawal in year one, climbing every year after as the divisor shrinks.

Now layer it. At 70 their combined Social Security is roughly $84,000/year. Add the $68,000 RMD, plus dividends. Their taxable income jumps past $150,000 — pushing the top of their income into the 24% bracket, where the bridge-year conversions would have been taxed at 12–22%. Worse, with combined income that high, 85% of their Social Security is taxable (the MFJ 85% threshold is just $44,000 of combined income; 1983 levels, not indexed). The conversions they skipped now arrive as RMDs that also drag their benefits into tax. That stacking is the “tax torpedo,” and it is exactly what the bridge years let you defuse.

The IRMAA cliff most people miss

Roth conversions raise your modified adjusted gross income (MAGI), and Medicare uses MAGI from two years prior to set your Part B and Part D premiums through the Income-Related Monthly Adjustment Amount (IRMAA). For 2026 the first MFJ cliff sits at $206,000 of MAGI (single: $103,000). Cross it by even $1 and each spouse’s Part B premium jumps from $185.00 to $259/month (an extra $74 each), plus a $13.70 Part D surcharge each — roughly $2,100 of extra Medicare cost for the couple that year (CMS 2026).

This is why Margaret and Tom cap conversions at $100,000 instead of filling the 22% bracket to the brim. Their MAGI stays near $114,000 — comfortably under the $206,000 cliff. The discipline is: convert aggressively, but model your MAGI against the IRMAA tiers before you hit “confirm.”

Source: CMS Medicare Premiums & Cost Sharing 2026. Note the two-year lookback — a conversion at 65 affects your Medicare premium at 67. If you convert before enrolling in Medicare at 65, that lead time is a feature: front-loaded conversions in your early 60s land before the IRMAA lookback window even opens.

How to sequence the five bridge years

1. Live on taxable cash and brokerage first. Spending from cash and the brokerage account does not add ordinary income (only realized gains do). That keeps the bottom of your brackets empty for conversions.
2. Project your full-RMD-era tax rate. Estimate the RMD at 73 on your projected balance (prior-year-end balance ÷ 26.5) plus your age-70 Social Security. If that future rate is 24%+, converting now at 12–22% is pure arbitrage.
3. Fill the bracket you choose, to a dollar. Decide whether you are filling to the top of 12%, 22%, or 24%, then convert exactly enough to reach it — no more. Recompute every year because the conversion itself shrinks next year’s RMD.
4. Check the IRMAA cliff before confirming. Keep MAGI under the relevant tier ($206K MFJ / $103K single, 2026) unless the conversion benefit clearly exceeds the two-year premium bump.
5. Pay the tax from outside the IRA. Use brokerage or cash to pay the conversion tax. Paying it from the IRA shrinks the amount that gets to grow tax-free and, before 59½, can trigger a penalty.
6. Execute by December 31. Conversions count in the calendar year the money moves — not April 15 like contributions. Miss the date and you lose that bridge year forever.

What most people get wrong

Myth: “I’ll just convert after I start Social Security — the money is still there.” It is, but the tax cost is not the same. Once benefits start, every conversion dollar can push more of your Social Security into the taxable column (up to 85%), so the effective rate on a conversion can spike well above its nominal bracket. The benefit-free bridge years are the only time you can convert without that interaction.

Myth: “Delaying Social Security and converting are separate decisions.” They are joined at the hip. The delay is what creates the empty-bracket window. If you claim at 62, you get a 30% reduced benefit and you fill your brackets with taxable benefits starting immediately — closing the conversion window before it opens. The 8%/year delayed credit and the conversion arbitrage compound in the same direction.

Myth: “Recharacterization lets me undo it if I convert too much.” No longer true. The TCJA eliminated recharacterization of conversions. Once you convert, it is permanent — which is exactly why you model the bracket and the IRMAA cliff before you click, not after.

Myth: “Roth conversions have RMDs too.” Roth IRAs have no lifetime RMDs for the original owner. That is the structural win: every dollar you move out of the traditional IRA during the bridge is a dollar that will never be forced out at 73 and never inflate your MAGI for IRMAA.

The lever: how to decide your number this year

The decision is not “should I convert” — if you are delaying Social Security to 70 and your projected RMD-era bracket is 24% or higher, the answer is yes. The decision is how much, and it comes down to one comparison: the bracket you fill today versus the bracket your future RMDs plus Social Security will land in. Fill the gap between them.

For Margaret and Tom, today’s rate is 12–22% and tomorrow’s is 24%+. Converting $100,000 a year for five years moves $500,000 across that spread, shrinks the RMD that would have hit at 73, keeps their MAGI under the $206,000 IRMAA cliff, and builds a tax-free Roth bucket they can draw from in any high-spending year without adding a dime to their MAGI. Run your own version of the bracket-fill table above, set your number, and execute it before December 31 — each bridge year you skip is gone for good.