IRMAA 2027 brackets: the law's formula puts the first one at $112,000 ($224,000 joint)
Medicare's income-related monthly adjustment amounts (IRMAA) for 2027 will be based on your 2025 income, and the brackets are set by a formula in the law: the 2018-based dollar amounts grow with the consumer price index (CPI-U) through August 2026, rounded to the nearest $1,000. Run on the published CPI, the formula reproduces CMS's 2026 brackets exactly. For 2027 it gives a first bracket of $112,000 for individual returns and $224,000 for joint returns. The next three brackets move by $1,000 (individual) depending on how CMS handles October 2025, a month for which the Bureau of Labor Statistics published no CPI.
- The formula: each amount is increased by the percentage by which the CPI-U average “for the 12-month period ending with August of the preceding calendar year exceeds such average for the 12-month period ending with August 2006 (or, in the case of a calendar year beginning with 2020, August 2018)”. Then: “such dollar amount shall be rounded to the nearest multiple of $1,000”.
- Which income: the law uses income “for the individual's last taxable year beginning in the second calendar year preceding the year involved”, so 2025 for 2027.
- The top bracket stays at $500,000 ($750,000 joint): CMS writes that these thresholds are to “be inflation-adjusted beginning in 2028”.
- The gap: BLS: “BLS did not collect survey data for October 2025 due to a lapse in appropriations.” The law does not say how to average twelve months with one missing.
- To see what the 2027 Part B premium does to a Social Security check, use our COLA 2027 calculator.
2026 brackets and the 2027 estimate
| Bracket starts above (individual / joint) | 2026 (CMS) | 2027 if October 2025 is filled in | 2027 if October 2025 is left out | |
|---|---|---|---|---|
| Tier 1 | $109,000 / $218,000 | $112,000 / $224,000 | $112,000 / $224,000 | Same either way |
| Tier 2 | $137,000 / $274,000 | $141,000 / $282,000 | $142,000 / $284,000 | Depends on October 2025 |
| Tier 3 | $171,000 / $342,000 | $176,000 / $352,000 | $177,000 / $354,000 | Depends on October 2025 |
| Tier 4 | $205,000 / $410,000 | $211,000 / $422,000 | $212,000 / $424,000 | Depends on October 2025 |
| Top tier | $500,000 / $750,000 | $500,000 / $750,000 | $500,000 / $750,000 | Fixed until 2028 |
The same method gives CMS's 2026 brackets
The CPI-U averaged 319.2050 over September 2024 to August 2025 and 249.2802 over September 2017 to August 2018. Multiplying $85,000, $107,000, $133,500 and $160,000 by the ratio and rounding gives $109,000, $137,000, $171,000, $205,000, the 2026 brackets in CMS's notice: “for 2026,” the threshold amounts are “$109,000 for a beneficiary filing an individual income tax return and $218,000 for a beneficiary filing a joint tax return”.
The missing month
For Treasury Inflation-Protected Securities, a regulation tells Treasury what to do when a CPI is missing: “If the CPI for a particular month is not reported by the last day of the following month, we will announce an index number based on the last available twelve-month change in the CPI.” Treasury's figure for October 2025 is 325.604, which is September 2025's 324.800 grown at the September-to-September rate for one month. Medicare's statute has no such rule. Filling October with Treasury's figure or with the midpoint of September and November leads to the same 2027 brackets; leaving October out raises brackets two to four by $1,000 each. CMS's notice with the 2027 premium will show which it used, and we will update this page then.
| Month | CPI-U (not seasonally adjusted) | Published by |
|---|---|---|
| Sept. 2025 | 324.800 | BLS |
| Oct. 2025 | 325.604 | Treasury fallback; BLS published none |
| Nov. 2025 | 324.122 | BLS |
| Dec. 2025 | 324.054 | BLS |
| Jan. 2026 | 325.252 | BLS |
| Feb. 2026 | 326.785 | BLS |
| March 2026 | 330.213 | BLS |
| April 2026 | 333.020 | BLS |
| May 2026 | 335.123 | BLS |
| June 2026 | 333.952 | BLS |
| July 2026 | 333.918 | BLS |
| Aug. 2026 | 334.980 | BLS |
Part D uses the same brackets
The Part D income-related amount uses the same income brackets; Social Security's tables for 2026 list both. The dollar amounts you pay in each bracket for 2027 depend on the 2027 Part B premium and the Part D national base premium, which are not published yet.
Rechecks and changes
- . First published, before CMS's 2027 notice.
Sources: 42 U.S.C. 1395r (2024 edition, govinfo); CMS, 2026 Part B premiums and deductible notice (Federal Register, Nov. 19, 2025); SSA, POMS HI 01101.020, IRMAA Sliding Scale Tables; BLS, CPI release for November 2025 (Dec. 18, 2025); Treasury FiscalData, TIPS and CPI Data (reference CPI); 31 CFR part 356, appendix B (TIPS). Dollars Ahead is not affiliated with Medicare, CMS or the Social Security Administration. This page shows what the published formula and data give. It is not an official figure; CMS's notice is the final word.