the trick with IRA -> Roth IRA
Mar. 7th, 2026 04:46 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
juan_gandhiI am sorry, I lost the content of my lost post, but in short, if you think it makes sense to talk about IRA/Roth IRA, just let me know, I'll rewrite my post.
By mistake, I've overwritten the previous version of my text with what ChatGPT said - so, sorry about the lost content...
(<a href="https://chatgpt.com/c/69ac95da-6620-8329-a14d-2af78bb21f7e">src</a>):
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I took a look at your post — interesting read. You’re essentially describing the IRMAA “cliff” effect and how it interacts with Roth conversions, which is exactly the subtlety many people miss.
A key piece of the puzzle is the Medicare surcharge called IRMAA (Income-Related Monthly Adjustment Amount), administered through the Centers for Medicare & Medicaid Services. It increases Medicare Part B and Part D premiums if your Modified Adjusted Gross Income (MAGI) exceeds certain thresholds.
The non-intuitive part you wrote about
Unlike income tax brackets, IRMAA works like cliffs.
If a married couple filing jointly goes even $1 over a threshold, the higher premium tier applies for the entire year.
For example (approximate recent numbers):
| MAGI (MFJ) | Medicare effect |
|---|---|
| ≤ $212,000 | standard premium |
| $212,001–$266,000 | first IRMAA tier |
| $266,001–$334,000 | second tier |
So if your income is:
$211,999 → normal premium
$212,001 → higher premium for the whole year
That’s why Roth conversions can create strange optimization problems:
the true marginal cost of an extra dollar can jump dramatically if it crosses an IRMAA boundary.
Why your observation is important
A Roth conversion increases AGI for that year, which is exactly what IRMAA uses.
And Medicare looks at your tax return from two years earlier when setting premiums.
So:
2024 income → 2026 Medicare premiums
That delay is what makes the planning tricky.
The implication for your “fill the bracket” idea
Your insight is correct:
Sometimes the optimal conversion is not the top of the tax bracket, but rather:
min( top_of_tax_bracket,
IRMAA_threshold − current_income )
because crossing the IRMAA line can add thousands in premiums over the following years.
Philosophically speaking
The planning problem becomes a small optimization problem:
You are balancing three marginal costs:
Income tax bracket
IRMAA cliff
Future RMD tax risk
That’s why people who think carefully about it (as you did) often end up doing moderate annual conversions, not huge ones.
