Before you start

An SSN or ITIN
Form W-4 with your employer for federal withholding
Massachusetts Form M-4 for state withholding
Form MA 1099-HC from your insurer, required to file the state return
Records of foreign income and foreign financial accounts

Step-by-step

1
Complete the W-4 and M-4 on day one
These set your federal and Massachusetts withholding. Getting them wrong is the most common cause of an April surprise, particularly in a two-income household.
Via employerWho: YouFirst week of employment
2
Determine your US tax residency
The substantial presence test counts weighted days over three years to decide whether the US taxes your worldwide income or only US-source income. Certain students and scholars are exempt from counting days for a period — relevant to a very large share of arrivals in this city.
OnlineWho: You
3
Check for an applicable tax treaty
The US has income tax treaties with around 70 countries which can reduce or exempt tax on specific income types, particularly for students, researchers and short assignments. Given Boston's research population this matters more here than almost anywhere — and treaty benefits are claimed on your return, not granted automatically.
OnlineWho: You
4
Model the surtax if you expect a one-off gain
The 4% surtax applies to taxable income above $1,107,750 for tax year 2026. It is assessed on total taxable income, so a company sale, a large equity vest or a property sale can cross the threshold in a year when your salary alone would not. Plan the timing before the transaction, not after.
OnlineWho: You
5
File federal and Massachusetts returns by 15 April
The tax year is the calendar year. You need Form MA 1099-HC from your insurer to evidence compliance with the health insurance mandate on the state return — without it, filing is awkward. An extension moves the filing date, not the payment date.
OnlineWho: YouBy 15 April annually
6
File an FBAR if foreign accounts exceed $10,000
Aggregate foreign account balances over $10,000 at any point in the year trigger a FinCEN filing, separate from your tax return. A normal current account at home is enough to cross it — and in a city full of international academics, this is very commonly missed.
OnlineWho: You

Documents you’ll need

Form W-2 from each employer, issued by 31 January
Form 1099s for freelance, interest and investment income
Form MA 1099-HC from your health insurer, required for the state return
Passport and travel history for the substantial presence day count
Foreign account statements for FBAR reporting

Things most newcomers don’t know

The surtax threshold is $1,107,750 for 2026 and it moves every year.

It began at $1 million when the 2022 ballot measure passed and is indexed for inflation annually. Anyone planning around it must use the current year's figure — quoting 'the million-dollar tax' is now wrong by over $100,000, and the gap widens each year.

Source: Mass.gov — Massachusetts 4% surtax on taxable income

The surtax catches one-off events, not just high salaries.

It applies to taxable income above the threshold, whatever the source. Selling a stake in a company, a large RSU vest or a property sale can push a single year over the line for someone whose salary is nowhere near it. In a city with this much biotech equity, that scenario is common — and the timing of a transaction across a year boundary can be worth a great deal.

Source: Mass.gov — surtax examples and instructions

A flat 5% is genuinely competitive for a high earner.

Compare against California's 13.3% top rate plus uncapped SDI, or New York's 9.65% state rate plus up to 3.876% to the city. Below the surtax threshold, Massachusetts is the cheapest of the three high-tax states in this set by a wide margin — a fact obscured by its reputation as 'Taxachusetts', which dates to a rate structure abolished decades ago.

Source: Mass.gov — Massachusetts tax rates

You need the MA 1099-HC to file, and it is easy to lose in a move.

The form evidences your compliance with the state health insurance mandate. Insurers post it in January, and people who moved mid-year frequently have it sent to an old address by a prior insurer. Update your address with any insurer you leave behind before January.

Source: Mass.gov — health care reform for individuals

Common mistakes to avoid

Using $1 million as the surtax threshold — it is indexed and stood at $1,107,750 for tax year 2026.
Triggering the surtax with a one-off sale or vest without planning the timing.
Assuming a federal treaty exemption flows through automatically to the state return.
Filing without Form MA 1099-HC and being unable to evidence mandate compliance.
Missing the FBAR — very commonly overlooked among international academics here.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.