Short answer: A nontaxable conversion generally should not raise AGI much. A taxable conversion, including one affected by the pro-rata rule, can raise Medicare MAGI.
Why the label is not enough
Reddit questions often ask whether a backdoor Roth counts for IRMAA. The better question is: how much of the conversion is taxable? IRMAA follows income, not the nickname of the strategy.
The pro-rata rule problem
If you have pre-tax IRA money, the pro-rata rule can make part of a conversion taxable even when you also made nondeductible IRA contributions. That taxable amount can increase AGI and Medicare MAGI.
Read the Roth conversion guide
Education sponsor placement for Roth conversion planning tools, tax planning education, or advisor-client resources.
What to check before converting
- Will any amount be taxable on Form 8606?
- Do you have pre-tax IRA balances that can trigger pro-rata taxation?
- Will taxable income push Medicare MAGI over an IRMAA threshold?
- Does the two-year lookback line up with the Medicare premium year you care about?
Next step: estimate a taxable Roth conversion and save the IRMAA planning checklist.