Best Accountants in Boston for the Massachusetts 4% Surtax in 2026

Best Accountants in Boston for the Massachusetts 4% Surtax in 2026

Here is the thing almost nobody gets right on the first try: the Massachusetts 4% surtax threshold does not double when you get married.

It is $1,107,750 for tax year 2026. One number. Single filer, joint filer, same number. And starting with tax year 2024, married couples who file jointly for federal purposes are required to file jointly in Massachusetts, so the obvious workaround was closed before most people found it. That is why the accountants in Boston for the Massachusetts 4% surtax who matter right now are the ones who see this coming a year out rather than the ones who compute it in April.

Most people who owe this tax owe it exactly once, in the year they sell something. Here is how the math actually works, three firms on Sam's List worth a call, and the four questions that tell you whether someone has done this before.

How We Picked These Firms

Methodology. Every firm below is a vetted member of the Sam's List directory with a live, public profile we checked on September 8, 2026. We selected on three stated criteria: relevance to a Massachusetts surtax question, published service lines that cover a one-time income spike, and a live profile with verifiable firm details.

The order reflects fit for a surtax question, not rank, score, or payment. Sam's List takes no referral fees and no commissions, and placement in this article is not sold. Where a firm has a meaningful number of verified client reviews, we cite the count shown on its live profile as of the date noted, and a review reflects one client's experience rather than a prediction of yours. Where a firm has few or no reviews, we describe it qualitatively instead and say so. This is not a ranking and it is not a recommendation of any firm for your situation.

What the Massachusetts 4% Surtax Actually Taxes

The short answer: only the slice above the line. Massachusetts personal income taxpayers pay an additional 4% on taxable income that exceeds the surtax threshold, and only on the excess. Cross the line by $50,000 and the surtax is $2,000, not 4% of everything.

The thresholds have moved every year since the Fair Share Amendment took effect:

Tax year	Surtax threshold
2026	$1,107,750
2025	$1,083,150
2024	$1,053,750
2023	$1,000,000

It applies to more filers than "millionaires tax" suggests. Individuals, trusts, estates, and unincorporated associations are all in scope, which means Form 1, Form 1-NR/PY, Form 2, Form M-990T-62, and Form 3M.

Layered on the 5% base rate, income above the line is taxed at 9%. Short-term capital gains, already taxed at 8.5%, reach 12.5%.

The Part-by-Part Rule That Surprises Sellers

Taxable income for surtax purposes is the sum of your Part A, Part B, and Part C taxable income, and any part that is negative is treated as zero.

Read that twice, because it removes a lever people assume they have. Part A is short-term gains, collectibles gains, and most interest and dividends. Part B is everything else. Part C is long-term capital gains. Once each part is computed, a loss in one cannot reduce another for surtax purposes.

So a year with a large long-term gain in Part C and an ugly operating loss in Part B does not net down to something under the threshold. The Part C number stands on its own. Losses can still offset within a part to the extent the statute allows, but not across parts.

Your House Counts

There is no separate surtax exclusion for the sale of a personal residence. To the extent gain on your home is included in Massachusetts taxable income, it is included in the surtax calculation too.

For a couple who bought in Cambridge or Somerville twenty years ago, that is not a hypothetical. The federal exclusion still does its work first, and only what remains flows through. But what remains is often large, and it lands in a single year alongside whatever else happened that year.

The planning question is almost never "how do I avoid this." It is "what else is landing in the same year, and can any of it move."

The One Real Spreading Lever

Installment sale income is counted for the surtax only as it is included in Massachusetts income under the installment sale rules in M.G.L. c. 62, § 63.

That is the lever. A seller who takes payments across three years generally brings the income into Massachusetts across three years, and three smaller numbers may each sit closer to or under the threshold than one large one. Three years of $900,000 is a very different surtax outcome than one year of $2.7 million.

The trade-offs are real and worth naming. You are taking credit risk on the buyer, you are betting the threshold and the rate do not move against you, and federal rules including the interest charge on large deferred balances may apply. If you want the mechanics first, see What Is an Installment Sale and How Is It Taxed. This is a structuring decision that belongs in the purchase agreement, not in the return.

One more operational detail: everyone subject to the surtax must file and pay electronically, and a nonresident whose taxable income exceeds the threshold has to file a Form 1-NR/PY even if they otherwise participate in a composite return.

1. Anomaly CPA, for Boston Founders and Investors Who Want the Planning Done Early

Anomaly CPA is a Boston accounting and tax strategy firm founded in 2018, now 21 people, serving clients nationwide and holding CPA and Enrolled Agent credentials. The practice is built around three groups: owners of high-growth businesses, venture-backed early-stage startups, and active real estate investors.

Anomaly CPA has a small number of client reviews on its Sam's List profile, and one of the entries shown there is flagged on the profile itself as a publicly shared social post rather than a verified client review, so we are not citing a review count for this firm. What we can point to is the shape of the practice.

That shape matters for a surtax question. The firm's stated strengths include equity compensation, K-1 complexity, and QSBS, which is the exact list of things that produce a one-year income spike in Massachusetts. A firm that runs year-round planning rather than annual compliance is the kind that can tell you in June that December is going to be expensive.

The gate is size. Published minimums are $400,000 in income or $1 million in revenue, and the model is a subscription rather than a per-return fee. If you need one return prepared for one unusual year, say that on the first call and ask what that costs, because a planning-led engagement is priced for planning.

2. Steady Co, for Sellers Where Massachusetts Is One State of Several

Steady Co is a Utah accounting, tax, and fractional CFO firm founded in 2024, now 15 people, built on roughly 30 years of Big Four and industry experience and serving businesses in all 50 states.

Steady Co has 15 verified client reviews on Sam's List as of 2026-09-06. Each review is submitted by an individual who identifies as a client of the firm and rates it on communication, subject-matter knowledge, and overall satisfaction. Reviews reflect those individual experiences, do not represent an endorsement by Sam's List, and are not indicative of future results.

Steady Co is the fit when the surtax is one line in a bigger apportionment question. A seller who moved to New Hampshire eighteen months before closing, or who ran the business from Boston while living elsewhere, has a residency and sourcing problem before they have a surtax problem. Getting the residency answer wrong is a far more expensive mistake than getting the surtax arithmetic wrong.

The limitation is the obvious one: this is not a Massachusetts firm. Ask directly how many Massachusetts returns they touch, and who reviews them.

3. Iota Finance, for Investors and Founders Who Want the Count Behind the Advice

Iota Finance is a Florida-based accounting and tax firm founded in 2022 that serves clients nationwide, working with small and mid-sized business owners, venture-backed companies, real estate investors, and high-net-worth individuals.

Iota Finance has 14 verified client reviews on Sam's List as of 2026-09-06. Each review is submitted by an individual who identifies as a client of the firm and rates it on communication, subject-matter knowledge, and overall satisfaction. Reviews reflect those individual experiences, do not represent an endorsement by Sam's List, and are not indicative of future results.

For a surtax question, the relevant thing about Iota's client mix is that it spans both sides of the problem. The surtax is triggered by an event, usually a sale, and the event sits inside an entity. A firm that reads the K-1 and the personal return as one document is the firm that notices the Part C number before it is final.

The trade-off is distance. A nationwide firm outside Massachusetts will not have the Department of Revenue relationships that matter if a notice arrives, so ask what happens then and who answers it.

The Three Side by Side

Firm	Based in	Published minimums	Best fit for
Anomaly CPA	Boston, MA	$400,000 income or $1M revenue	Boston founders and investors who want planning a year ahead
Steady Co	Vineyard, UT	$750,000 income and revenue	Sellers with a residency or multi-state sourcing question
Iota Finance	Florida, serves nationwide	None published	Investors and founders who want the entity and the 1040 read together

Four Questions to Ask Accountants in Boston About the Massachusetts 4% Surtax

Ask them to walk you through Part A, Part B, and Part C for your situation and tell you which one carries the surtax. Ask what your projected surtax number is for this year and next, in dollars. Ask whether an installment structure is available on your transaction and what it costs you elsewhere. And ask who prepares the Schedule 4% Surtax and who reviews it.

Anyone who answers all four in plain language has done this before. If you want to compare a few firms first, browse the Sam's List accountant directory, or start with the broader Boston list.

Frequently Asked Questions

What is the Massachusetts 4% surtax threshold for 2026? $1,107,750. Only taxable income above that amount is subject to the additional 4%. The threshold was $1,083,150 for 2025, $1,053,750 for 2024, and $1,000,000 for 2023, because it is adjusted annually for inflation.

Does the surtax threshold double for married couples filing jointly? No. The threshold is the same amount regardless of filing status. Beginning with tax year 2024, married couples who file jointly for federal purposes are generally required to file jointly in Massachusetts, and there is no exception for couples subject to the surtax, including couples with different residency status.

Is the gain on selling my home subject to the 4% surtax? To the extent the gain is included in your Massachusetts taxable income, yes. There is no separate surtax exclusion for a personal residence. The federal exclusion applies first, and any remaining taxable gain is counted in the year of sale.

Can a business loss offset a capital gain for surtax purposes? Not across parts. Taxable income for the surtax is the sum of Part A, Part B, and Part C, and any part that is negative is treated as zero. A loss can reduce income within a part to the extent the statute allows, but once each part is determined, a negative amount in one part cannot reduce another.

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About the author: Kimberly Green is the cofounder of Sam's List, where business owners and high earners find vetted CPAs, financial advisors, and fractional CFOs. She's met one-on-one with 400+ financial professionals and writes from the real data behind thousands of client-advisor matches. Ask her anything about finding an accountant - she's heard it all, including the questions people are afraid to ask.