In general, we will use modified adjusted gross income information from IRS to determine your income-related monthly adjustment. We will make retroactive adjustments to your income-related monthly adjustment amount as described in paragraphs (a), (b), and (d) of this section.

(a) When we have used modified adjusted gross income from the tax year 3 years prior to the effective year as described in §418.1135(b), and IRS provides modified adjusted gross income information from the tax year 2 years prior to the effective year, we will use the new information to make an initial determination for the effective year. We will make retroactive adjustments back to January 1 of the effective year, or the first month you were enrolled or reenrolled in Medicare Part B if later than January.

(b) When we have used the modified adjusted gross income information that you provided for the tax year 2 years prior to the effective year and the modified adjusted gross income information we receive from IRS for that same year is different from the information you provided, we will use the modified adjusted gross income information provided to us by IRS to make a new initial determination. We will make retroactive adjustments back to January 1 of the effective year, or the first month you were enrolled or reenrolled in Medicare Part B if later than January.

(c) When we have used information from your amended Federal tax return that you provide, as explained in §418.1150, or you provide proof that the information IRS provided to us is incorrect as described in §418.1335, we will not make any adjustments to your income-related monthly adjustment amount for the effective year or years based on IRS information we receive later from IRS.

(d) When we use modified adjusted gross income information that you provided due to a qualifying life-changing event and we receive different information from IRS, we will use the IRS information to make retroactive corrections to all months in the effective year(s) during which you were enrolled in Medicare Part B, except when paragraph (c) of this section applies.

(e) When we used the table in §418.1120(b)(3) to determine your income-related monthly adjustment amount, and you lived apart from your spouse throughout that year, we will ask you for a signed statement or attestation that you lived apart from your spouse throughout that year. We will also ask you to provide information about the addresses of you and your spouse during that year. If you provide a signed statement or attestation that you lived apart from your spouse throughout that year, and information about your respective addresses that year, we will use the table in §418.1120(b)(1) to determine your income-related monthly adjustment amount.