20 C.F.R. § 418.1110 – What is the effective date of our initial determination about your income-related monthly adjustment amount?

(a) Generally, an income-related monthly adjustment amount will be effective for all months that you are enrolled in Medicare Part B during the year for which we determine you must pay an income-related monthly adjustment amount. We will follow the rules in 42 CFR part 408, subpart C, regarding premium collections to withhold your income-related monthly adjustment amount from a benefit payment or to determine if you will be billed directly.
(b) When we have used modified adjusted gross income information from IRS for the tax year 3 years prior to the effective year to determine your income-related monthly adjustment amount and modified adjusted gross income information for the tax year 2 years prior later becomes available from IRS, we will review the new information to determine if we should revise our initial determination. If we revise our initial determination, the effective date of the new initial determination will be January 1 of the effective year, or the first month you were enrolled or re-enrolled in Medicare Part B if later than January.
(c) When we use your amended tax return, as described in § 418.1150, the effective date will be January 1 of the year(s) that is affected, or the first month in that year that you were enrolled or reenrolled in Medicare Part B if later than January.
Example:You are enrolled in Medicare Part B throughout 2011. We use your 2009 modified adjusted gross income as reported to us by IRS to determine your 2011 income-related monthly adjustment amount. In 2012 you submit to us a copy of your 2009 amended tax return that you filed with IRS. The modified adjusted gross income reported on your 2009 amended tax return is significantly less than originally reported to IRS. We use the modified adjusted gross income that was reported on your 2009 amended tax return to determine your income-related monthly adjustment amount. That income-related monthly adjustment amount is effective January 1, 2011. We will retroactively adjust for any differences between the amount paid in 2011 and the amount that should have been paid based on the amended tax return.
(d) When we use evidence that you provide which proves that the IRS modified adjusted gross income information we used is incorrect, as described in § 418.1335, the effective date will be January of the year(s) that is affected or the first month in that year that you were enrolled or reenrolled in Medicare Part B if later than January.
(e) When we use information from a more recent tax year that you provide due to a major life-changing event, as described in § 418.1201, the effective date is described in § 418.1230.