The Massachusetts short-term capital gains tax rate is 8.5%, a flat rate that applies to profits from selling capital assets you held for one year or less.1Mass.gov. Massachusetts Tax Rates That is well above the 5% rate the state applies to ordinary income and long-term gains, and high earners can owe an additional 4% surtax on top of it. The rate dropped from 12% in 2023 as part of a broader tax relief package.2Massachusetts Department of Revenue. 2023 Massachusetts Tax Cuts Legislation
What Counts as a Short-Term Gain
A gain is short-term if you owned the asset for one year or less before selling. Capital assets include stocks, bonds, mutual fund shares, real estate, and most other investment or personal property. Hold the asset for more than one year and the gain is long-term, taxed at 5% instead.3Massachusetts Department of Revenue. TIR 02-21 – Capital Gains and Losses – Massachusetts Tax Law Changes
The holding period starts the day after you acquire the asset and runs through the day you sell. A single day can be the difference between an 8.5% tax bill and a 5% one. Stock bought on March 10, 2025 needs to be held until at least March 11, 2026 for the gain to count as long-term. Sell on March 10, 2026 and you have held it for exactly one year, which Massachusetts still treats as short-term.
Calculating What You Owe
Start with your cost basis, which is what you paid for the asset including purchase commissions. Subtract that from the sale price to get your gain. Buy 100 shares at $50 each, sell them seven months later at $70 each, and your short-term gain is $2,000. Multiply by 8.5% and you owe Massachusetts $170.
Taxpayers whose total taxable income exceeds roughly $1,083,150 for tax year 2025 owe an additional 4% surtax on the portion above that threshold, which adjusts annually for inflation.4Mass.gov. Massachusetts 4% Surtax on Taxable Income Short-term gains count toward that threshold. If a large sale pushes your total income past the line, the excess is effectively taxed at 12.5% at the state level. Voters approved the surtax in 2022, and it catches more sellers than you might expect in a year with a big liquidation.
Offsetting Gains With Losses
You can reduce short-term gains by netting them against capital losses from the same tax year. Short-term losses offset short-term gains dollar for dollar. When losses exceed gains, you can apply up to $2,000 of the excess against interest and dividend income.5Mass.gov. Differences Between MA and Federal Tax Law for Personal Income Anything still left over can offset long-term capital gains.6General Court of Massachusetts. An Act Enhancing State Revenues
Massachusetts does not let you deduct capital losses against wages or other earned income, unlike the federal $3,000 annual allowance. The losses stay inside the investment income categories. The state does allow unused losses to carry forward indefinitely until you use them up.7Mass.gov. TIR 87-10 – Capital Loss Carryovers – Transition Rules A bad year in the market can chip away at future gains for as long as the carryover lasts, which makes careful recordkeeping worth the trouble.
How to Report and When to File
Short-term gains go on Schedule B (Interest, Dividends and Certain Capital Gains and Losses), filed with your Form 1 state return. Enter the gross short-term gains from your federal Schedule D on Line 10 of Massachusetts Schedule B.8Mass.gov. 2025 Schedule B – Interest, Dividends and Certain Capital Gains and Losses Massachusetts Schedule D is for long-term gains and losses, not short-term ones.
You will need the acquisition date, sale date, cost basis, and sale proceeds for each transaction. Your brokerage sends a 1099-B with that information, but check it against your own records, especially after share transfers between accounts or shares received through an employer plan.
Tax year 2025 returns are due April 15, 2026. Massachusetts grants an automatic six-month filing extension, but only if you have paid at least 80% of your total tax liability by the original due date through withholding, estimated payments, or a payment submitted with Form M-4868.9Department of Revenue Commonwealth of Massachusetts. 2025 Massachusetts Form 1 Instructions Fall short of 80% and the extension is invalid, with penalties accruing from April 15.
Estimated Tax Payments on Capital Gains
If you expect to owe more than $400 in Massachusetts income tax that is not covered by withholding, you must make quarterly estimated payments.10Mass.gov. Massachusetts DOR Personal Income and Fiduciary Estimated Tax Payments This trips up a lot of people who sell stock during the year. Nobody withholds tax on a brokerage account gain.
Quarterly due dates for tax year 2026:
- First quarter: April 15, 2026
- Second quarter: June 16, 2026
- Third quarter: September 15, 2026
- Fourth quarter: January 15, 2027
To avoid an underpayment penalty you generally need to pay at least 80% of your annual tax liability before you file. There is also a safe harbor: if your estimated payments plus withholding equal or exceed your total tax from the prior year, Massachusetts will not penalize you for underpaying even if you owe more this year.10Mass.gov. Massachusetts DOR Personal Income and Fiduciary Estimated Tax Payments That prior-year safe harbor is especially useful when a large, unexpected gain lands in the middle of the year.
Penalties for Paying Late
Massachusetts charges 1% per month on taxes not paid by the deadline, up to a maximum of 25%, plus a separate 1% per month penalty capped at 25% for filing late.12Mass.gov. Massachusetts Penalties and Interest Assessed by DOR They run concurrently, so filing late and paying late effectively doubles the monthly hit.
On top of the penalties, the Department of Revenue charges interest on unpaid balances. For the first quarter of 2026, the rate is 8%, compounded daily.13Mass.gov. TIR 25-8 – Interest Rate on Overpayments and Underpayments The rate adjusts each quarter based on the federal short-term rate plus four percentage points. Interest accrues from the original due date regardless of whether you filed an extension, which is why the 80% payment rule matters so much.
How Federal Tax Affects the Total
The IRS taxes short-term gains as ordinary income, so the federal rate on those gains tracks your overall bracket and can run from 10% to 37%.14Internal Revenue Service. Topic no. 409, Capital Gains and Losses Massachusetts applies its 8.5% rate regardless of income level, aside from the surtax, so the state and federal calculations are independent.
Massachusetts generally starts with the same cost basis you use federally, though there are exceptions for inherited property and gifts where state adjustments differ.15Mass.gov. TIR 88-7 – New Massachusetts Basis Rules You cannot deduct Massachusetts income tax when calculating your state return, though you can deduct state taxes on your federal return if you itemize, subject to the $10,000 SALT cap.
Combine the two layers and a short-term gain in Massachusetts can easily hit 30% in total tax for middle-income earners, and closer to 50% for high-income taxpayers facing both the federal top bracket and the state surtax. Running those numbers before you sell is the single most important piece of planning for a short-term gain.