Clear Money Guide
What this state guide covers
A quick view of the questions, practical details and source notes below.
Updated August 12, 2026. Quick answer: Partly — but for most converters that means yes. Massachusetts includes the federally taxable part of a conversion in state income at its flat 5% rate, 9% above roughly $1.1 million with the surtax, and has no age-based retirement exclusion that could shelter it. The one real exception is basis: contributions Massachusetts has already taxed come out first and are not taxed again.
Confidence note: high on the rate and on the absence of an age-based exclusion; what varies between converters is how much previously-taxed Massachusetts basis the traditional IRA actually holds.
Why a conversion is a different question from a withdrawal
Almost every state summary answers “how does Massachusetts tax retirement income?” That is a question about distributions. A Roth conversion is not a distribution in the ordinary sense — it is a voluntary election to recognise income now in exchange for tax-free growth later. Whether a state’s retirement exclusion reaches that election is a separate question, and it is the one that decides your bill.
The exception here is not an exemption, it is basis. Massachusetts did not allow a deduction for traditional-IRA contributions the way the federal return did, so those already-taxed dollars come out tax-free first — and everything above them converts as ordinary income at 5%.
Two practical consequences. If you have contributed to a traditional IRA while a Massachusetts resident, the basis figure is worth reconstructing before you convert. And a large conversion can lift taxable income into the 9% surtax band, which is a rate change, not an exclusion question.
What Massachusetts does with the converted amount
State income tax: flat 5% plus 4% surtax on taxable income over ~$1,107,750 (2026, indexed) — effectively 2 brackets (5%/9%)
How Massachusetts treats IRA and plan income: Massachusetts state/local and U.S. government contributory pensions exempt (as are pensions from states with reciprocal treatment). Private pensions, 401(k), and traditional IRA distributions taxable at 5% (IRA/annuity basis from previously MA-taxed contributions recovered tax-free). Large lump sums can trigger the 9% surtax band.
Basis is what stops a Massachusetts conversion being taxed twice.
The federally taxable part of a conversion is state income at the flat 5%, and a large one can reach the 9% band. Contributions Massachusetts has already taxed come out first and are not taxed again, so knowing your basis is worth real money, and there is no age-based exclusion to fall back on if you do not.
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What to ask a preparer about Massachusetts
How much of my traditional IRA is previously-taxed Massachusetts basis, and will this conversion push income into the 9% surtax band?
Converting around a move
Converting in the year you move into Massachusetts is the case that catches people. Residency at the moment of conversion is what generally determines which state gets to tax it, so a conversion executed a week before a move and one executed a week after can produce different bills.
Four separate taxes change when you move, not one: income tax on withdrawals, treatment of Social Security, estate tax, and inheritance tax. A state that looks good on conversions can be worse on the other three.
The state bill is the smaller half
Whatever Massachusetts does, the conversion is federal ordinary income first. The federal bracket you land in, and whether the conversion pushes you over an IRMAA threshold two years later, will usually move more money than the state line does. The state answer tells you whether to convert here; the federal answer tells you how much to convert at once.
Paying the tax from outside the account matters more than either. Using converted dollars to pay the bill shrinks the balance that was the entire point of converting.
Sources
Authority: M.G.L. c. 62 § 2(a)(2)(E); Mass.gov: Tax Treatment of Government Pensions in Massachusetts; M.G.L. c. 65C, sec. 2A (as amended by St. 2023, c. 50).
Compiled from state statutes, session laws and revenue-department publications and adversarially verified in July 2026. Dataset confidence for Massachusetts: high.
This page states what the cited authority says. It is not tax advice, and a conversion large enough to matter is worth putting in front of a preparer who can see your whole return.
Nearby states
A flat rate with a surtax band above it means a large conversion and a small one are not taxed at the same rate, so enter the rate that applies to the band your conversion lands in. The Roth conversion state tax calculator then shows the state bill next to the federal one and how much of the conversion reaches the Roth.