Maybe some of this will help figure it out. 10/22/25 See this post for the 2025 IRMAA and the brackets
https://ttlc.intuit.com/community/file-with-turbotax/discussion/can-you-give-info-on-projected-irmaa...
Yes they look back a couple years to figure the IRMAA for the next year.
https://secure.ssa.gov/apps10/poms.nsf/lnx/0601101031
IRMAA uses your AGI plus tax exempt interest on 1040 line 2a.
SSA - POMS: HI 01101.010 - Modified Adjusted Gross Income (MAGI) - 01/05/2024
