How a Massachusetts paycheck works
Massachusetts starts from a flat rate, then adds a surtax at the very top. Withholding gets there in an order no other state uses. Your employer first subtracts what has already come out of your pay for Social Security and Medicare, up to a limit. Then it subtracts your exemptions. Then it applies the rate. Finally it takes fixed amounts off the tax itself for head of household and for blindness.
That first step is the unusual one. Most states start from your gross wage; Massachusetts starts from your wage minus part of your federal payroll tax.
Federal income tax withholding
Federal withholding annualises the wage, subtracts the standard deduction that matches the filing status on Form W-4 Step 1, applies the graduated schedule for that status, and deducts the dependent credit from Step 3. This page models a W-4 with Steps 2 and 4 left blank: one job, no spouse income, no other income, no extra withholding. Above the income limit for the status, the dependent credit tapers by a set amount for every thousand dollars of excess rather than disappearing at a cliff.
Social Security and Medicare
Social Security applies a flat rate to wages up to an annual ceiling that is re-indexed each year, so it stops partway through the year for a high earner. Medicare applies to every dollar, and above a fixed wage threshold the employer withholds the Additional Medicare tax on the excess, with no employer match and no regard for filing status.
The FICA deduction, and why it stops mattering
Step one of the state's method subtracts what you have had deducted for Social Security and Medicare, and caps the total it will subtract. Because those two together take a fixed slice of every pay packet, that cap is reached on a fairly modest salary. Above that point the deduction is simply the cap, the same figure for a nurse and a chief executive, and it stops growing with your pay.
Below that point it does grow, which softens the state tax a little for lower earners. It is the only place in the calculation where your federal payroll tax touches your state tax.
Exemptions are not just per head
Form M-4 exemptions work in a way that catches people out. Claiming one gets you a fixed amount. Claiming a second adds a smaller amount on top, and so does each one after that, because the annual figure is a base amount plus a per-exemption amount. The first exemption is therefore worth far more than the second.
The step is also all or nothing at the bottom. If you claim zero exemptions, the whole step is skipped, base amount included, and nothing at all is subtracted. Going from zero to one is the single largest change you can make to your Massachusetts withholding.
The low wage cliff
There is a wage below which an employee claiming at least one exemption has nothing withheld. Above it, the ordinary calculation applies in full straight away. There is no phase-in, so the first dollar over that line brings a whole year's worth of withholding with it, and take-home pay can fall as pay rises.
This page flags salaries where the next step would cross that line. Note that it applies only if you claim an exemption. An employee claiming none is withheld from the first dollar of pay, with no exempt band at all, which is the opposite of what most people expect.
The surtax at the top
Above a high annual threshold, indexed each year, income is taxed at the main rate plus a surcharge, and the withholding tables build both into a single schedule. The threshold is well above the range this page covers for most salaries, but it is in the calculation, so a salary large enough will show it.
Head of household and blindness come off the tax
Two adjustments are subtracted from the tax rather than from your wage: a fixed annual amount for filing as head of household, and another for each blind person, you and a blind spouse. Because they come off the tax, they are worth the same to every employee regardless of salary, unlike an exemption.
Local income tax
No Massachusetts city or town taxes wages. Boston, Worcester and Springfield all have the same payroll deductions as anywhere else in the state.
Paid family and medical leave
Massachusetts runs a paid family and medical leave programme funded partly by an employee contribution, which appears on real payslips as its own line. It is not included in this figure. Nor is the employer's share.
What the employer pays on top
The employer matches Social Security and Medicare and pays federal unemployment tax at its net rate. Massachusetts unemployment insurance, the employer medical assistance contribution and the employer share of paid family and medical leave are all priced per employer, so they are left out.
What this calculator assumes
The figure models a salaried employee paid evenly across the year with a standard Form W-4 and Form M-4, and no pre-tax deductions. It leaves out:
- Pre-tax contributions such as a 401(k), health premiums, HSA or flexible spending accounts, which reduce the wages subject to income tax and often to FICA.
- The employee share of the paid family and medical leave contribution.
- Extra withholding requested on the federal or state certificate, and the W-4 Step 2 and Step 4 adjustments.
- Bonuses and other supplemental wages, which have their own method in the circular.
- The exemption for a full-time student whose annual income stays under a set figure.
- Employer-side state contributions, which are priced per employer, and any federal unemployment credit reduction.
- Employees outside the normal Social Security system, such as some public-sector staff and certain visa holders.
Withholding versus your final tax bill
Withholding is a prepayment. The annual returns, federal and state, replace these standard assumptions with your real situation: itemised deductions, other income, and credits payroll knows nothing about. One job usually produces a refund; two jobs, a working spouse or investment income often produce a balance due.