Capital Gains on a Massachusetts Home Sale — Including the 4% Surtax

Selling a long-held Massachusetts home can trigger tax in two places at once: federal capital gains above the exclusion, and the Massachusetts 4% surtax on income above an annual threshold. The second one catches people, because it is relatively new, because it is indexed and therefore easy to misremember, and because a single large gain in a single year can push an otherwise ordinary household over the line.

Start with the part most sellers already know. Under federal law, a homeowner who has owned and used the property as a primary residence for at least two of the previous five years may exclude up to $250,000 of gain if single, or $500,000 if married filing jointly. Gain above that is taxable.

How does the Massachusetts surtax apply?

Massachusetts taxes long-term capital gains at its ordinary personal income tax rate. On top of that, the Fair Share Amendment — commonly called the millionaires tax — adds a 4% surtax on Massachusetts taxable income above an inflation-indexed threshold. For tax year 2026 the Massachusetts Department of Revenue set that threshold at $1,107,750.

Two things about it matter for home sellers.

It is marginal. Only the income above the threshold is taxed at the extra 4%. Crossing the line by a dollar does not retroactively tax everything below it. This is the most common misunderstanding and it causes unnecessary panic.

There is no special exemption for a home sale. The taxable portion of your gain — after the federal exclusion — is part of Massachusetts taxable income for the year, and counts toward the threshold along with your wages and everything else.

How do you calculate the gain?

Not sale price minus purchase price. The actual formula is:

Amount realized (sale price minus selling costs) minus adjusted basis (original purchase price plus capital improvements, minus any depreciation taken).

The adjusted basis is where sellers leave money on the table, because capital improvements raise your basis and therefore reduce your taxable gain — and almost nobody keeps the records.

Things that generally increase basis: additions, a new roof, replacement windows, a kitchen or bathroom renovation, a new heating system, landscaping and hardscaping, a finished basement. Things that generally do not: repairs and maintenance, painting, and anything you deducted elsewhere.

For a house owned for thirty years, the difference between a documented basis and an undocumented one can be very large. If you have owned a home a long time, reconstructing what you can from permits, contractor records, and bank statements is worth doing before you sell, not after.

Selling costs also reduce the amount realized — brokerage compensation, legal fees, and the deed excise tax, which in Massachusetts the seller customarily pays at $4.56 per $1,000 of sale price as of 2026. See the closing cost guide for the full list.

What are the legitimate ways to reduce exposure?

Document your basis. The single highest-return step, and it costs nothing but effort.

Confirm you meet the two-of-five-year test. Partial exclusions may be available for sales driven by a change in employment, health, or certain unforeseen circumstances even when the full test is not met.

Consider the timing. Because the surtax threshold applies per tax year, the year in which a sale closes can matter — particularly if you also have a bonus, an equity vesting event, or a business sale landing in the same year. A closing date is negotiable.

For investment property, look at a 1031 exchange. This does not apply to a primary residence, but for an investment or rental property it can defer the gain entirely. See our 1031 exchange guide.

Talk to a CPA before you list. Not after you have an accepted offer, when most of the useful options have already closed off.

What about inherited property?

Different rules, and much more favorable ones. Inherited property generally receives a stepped-up basis to its fair market value at the date of death, which can eliminate decades of accumulated gain. This is why a date-of-death appraisal matters so much for an estate, and why heirs who sell without one often overstate their gain. Our guide to selling an inherited property covers the process.

Figures are stated as of tax year 2026 and the threshold is indexed annually. This is general information, not tax advice — consult a CPA or tax attorney about your situation.