Medicare Increases due to Roth conversions

If you are asking about the Medicare surcharge, that has its own brackets. See here. 

https://kindnessfp.com/medicare-irmaa-brackets/#2024_Part_B_Medicare_IRMAA_Bracket

The link that Bsch4477 provided shows the IRMAA brackets for 2024.  It has also not been updated to show the 2025 IRMAA brackets that are now fully determined, so it is an outdated reference.

Your 2024 MAGI for the purpose affects your 2026 IRMAA and the IRMAA brackets for 2026 will not be known for certain until September 2025.  The following link provides guesses for the 2026 IRMAA brackets and gets updated every month when the CPI for the previous month is announced:

https://thefinancebuff.com/medicare-irmaa-income-brackets.html#htoc-2026-irmaa-brackets

@dmertz  How does it work when changing from Joint to Single?  My husband died in 2023.  

My IRMAA for 2024 of an extra 174.70 + 33.30 part D was right based on 2022.  Should I have told them I was Single in 2024?

Now for 2025 according to SS I'm not paying any IRMAA, just the basic $185.  But based on 2023 (Joint)  I should be paying IRMAA.  Or do they know husband died in 2023? 

UPDATE: Just noticed that my 2023 Joint MAGI is under the Standard Part B Premium amount, Whew.  

But actually my IRMAA should go way up since my Single MAGI is still the same or more than my Joint MAGI was.  My income didn't go down, I continue to get the same pension that my husband had (he had a good state pension).  So I get a free year before they use  my 2024 Single return for 2026?  

@VolvoGirl 

https://www.ssa.gov/medicare/lower-irmaa

The request can be made only if your income decreased as a result of a life-changing event, generally using the MAGI for the year following the year from which they would normally use the MAGI.  In your case, it seems that there is no decrease but there is instead effectively an increase based on the same MAGI but applied as Single instead of Married Filing Jointly.