Boston does not have a city income tax or a city business tax, which surprises founders arriving from New York or San Francisco. Almost every tax obligation a Boston startup carries is a Massachusetts obligation, administered by the Department of Revenue (DOR), the Department of Family and Medical Leave, the Department of Unemployment Assistance, and the Secretary of the Commonwealth. The one city layer is the personal property filing with Boston's Assessing Department.
That makes the Massachusetts stack simpler than New York's, but not light. The corporate excise has a $456 floor that never goes away. Sales tax applies to most SaaS. The state's paid family and medical leave program has its own quarterly filings, and it changes shape in 2027. And the 4 percent surtax on high incomes matters more to founders than almost any other state rule, because it lands in the year you sell.
This guide puts every Massachusetts and Boston deadline for 2027 on one page, then explains each obligation. For the federal and Delaware dates in more depth, see our complete 2027 startup tax calendar. Figures reflect what mass.gov, the Secretary of the Commonwealth, and boston.gov publish as of late 2026; confirm current figures before you file.
The Consolidated 2027 Calendar
Dates assume a calendar year Delaware C-corp with an office or employees in Boston. Weekend shifts are applied: January 30, January 31, July 31, October 30, and October 31 all fall on weekends in 2027.
| Date | Layer | What is due |
|---|---|---|
| Jan 15 (Fri) | Federal + MA | Q4 2026 personal estimated taxes for founders (federal 1040-ES and Massachusetts Form 1-ES) |
| Feb 1 (Mon) | Federal | W-2s to employees; 1099-NEC to contractors and the IRS (January 31 is a Sunday) |
| Feb 1 (Mon) | Massachusetts | Q4 2026 Form M-941 withholding return (quarterly filers); Q4 PFML contributions and wage report; Q4 unemployment insurance report; Q4 2026 sales tax return for quarterly filers |
| Mar 1 (Mon) | Delaware | Delaware franchise tax and annual report |
| Mar 1 (Mon) | Boston | State Tax Form 2 (Form of List) to the Boston Assessing Department, if you hold taxable personal property |
| Mar 15 (Mon) | Massachusetts | Annual report to the Secretary of the Commonwealth; first corporate excise estimated payment (40 percent) if you expect excise over $1,000 |
| Apr 15 (Thu) | Federal | Form 1120 or Form 7004 extension; Q1 federal corporate estimate |
| Apr 15 (Thu) | Massachusetts | Form 355 (or Form 355U for combined groups) with at least the $456 minimum, or extension with payment; founders' Form 1 |
| Apr 30 (Fri) | Massachusetts | Q1 M-941, PFML, unemployment insurance, and quarterly sales tax returns |
| Jun 15 (Tue) | Federal + MA | Q2 federal estimate; second excise estimate (25 percent) |
| Jul 30 (Fri) | Massachusetts | Q2 quarterly sales tax return |
| Aug 2 (Mon) | Massachusetts | Q2 M-941, PFML, and unemployment insurance (July 31 is a Saturday) |
| Sep 15 (Wed) | Federal + MA | Q3 federal estimate; third excise estimate (25 percent) |
| Oct 15 (Fri) | Federal + MA | Extended Form 1120 and extended Form 355 |
| Nov 1 (Mon) | Massachusetts | Q3 M-941, PFML, unemployment insurance, and quarterly sales tax returns (October 30 and 31 fall on a weekend) |
| Dec 15 (Wed) | Federal + MA | Q4 federal estimate; final excise estimate (10 percent) |
| 30th of each month | Massachusetts | Monthly sales tax returns, for vendors with more than $1,200 of annual sales tax liability |
Patriots' Day, a Massachusetts legal holiday, falls on April 19 in 2027, so it does not move the April 15 deadline this year.
Registering a Delaware Corp in Massachusetts
A Delaware corporation transacting business in Massachusetts files a Certificate of Registration with the Corporations Division of the Secretary of the Commonwealth under Chapter 156D, Section 15.03. The fee is $400, or $375 by fax, and guidance from the Division says to file within 10 days after you begin transacting business. You will need a certificate of good standing from Delaware.
Once registered, a foreign corporation files an annual report within two and a half months after its fiscal year ends, which is March 15 for calendar year companies. The fee is in the $100 to $125 range depending on filing method (check the Corporations Division fee schedule for the current amount), and late reports draw a $25 penalty. Like any state filing that is not tied to a tax return, it is easy to miss; a lapsed report can lead to involuntary revocation of your registration if ignored long enough.
The Massachusetts Corporate Excise: Form 355
A business corporation doing business in Massachusetts pays the corporate excise, which has two parts:
- Income measure. 8 percent of net income apportioned to Massachusetts.
- Non-income measure. $2.60 per $1,000 of taxable Massachusetts tangible property or, for intangible property corporations, net worth.
You pay the sum of the two, or the $456 minimum, whichever is greater. The minimum is never prorated, even for a first year that lasts a few weeks. For a startup losing money with laptops and a leased office, the non-income measure is usually small and the bill comes out to exactly $456.
Two details worth knowing:
- Nexus is broad. Physical presence clearly counts. Under DOR's regulations, substantial sales into the state can also create corporate excise nexus without an office (a bright line of $500,000 of Massachusetts sales is commonly cited; confirm against the current regulation if you are a remote seller).
- Combined reporting. Corporations in a unitary group, such as a Delaware parent with a subsidiary, generally file a combined report on Form 355U instead of separate Form 355s.
The return is due April 15 for calendar year C-corps. Massachusetts grants a six month extension, but the extension is void unless you have paid at least 50 percent of the total tax or the $456 minimum, whichever is greater, through estimates or with the extension request. In practice: pay the $456 by April 15 even when you are extending.
Estimated payments. Corporations that reasonably expect excise above $1,000 must pay estimates: 40 percent by the 15th day of the third month, 25 percent by the sixth, 25 percent by the ninth, and 10 percent by the twelfth. New corporations with fewer than 10 employees in their first full taxable year use different percentages. A startup paying only the minimum does not need to make estimates.
Massachusetts Sales Tax on SaaS
Massachusetts taxes the sale of prewritten software at the 6.25 percent statewide rate, with no local add-on, and that includes standardized software accessed remotely. The Supreme Judicial Court upheld the DOR's position on remote access software in Citrix Systems v. Commissioner of Revenue in 2020. Custom software is treated as a professional service and is not taxable. DOR has also published a working draft rewrite of its software regulation, 830 CMR 64H.1.3, so watch for the final version.
Mechanics:
- Registration. Register through MassTaxConnect before you make taxable sales. An in-state office means you are in from the start. Remote sellers must register once their Massachusetts sales exceed $100,000 in the current or prior calendar year.
- Multiple points of use. Business customers with users in several states can provide a multiple points of use certificate (Form ST-12) and self-assess apportioned use tax, which relieves you of collecting on that sale.
- Filing frequency. Annual if your sales tax liability is $100 or less, quarterly from $101 to $1,200, and monthly above $1,200. Returns are due on the 30th day after the period ends. Note how low the monthly line is: about $19,200 of taxable sales a year puts you on monthly filing, so most SaaS companies collecting Massachusetts tax will file 12 returns a year.
Usage-based and hybrid billing complicate the taxable amount; our guide to sales tax for usage-based pricing walks through it.
Massachusetts Payroll: Withholding, PFML, and UI
Income tax withholding. Massachusetts withholds at a flat 5 percent rate under Circular M. Filing frequency depends on your projected annual withholding: quarterly for $101 to $1,200, monthly for $1,201 to $25,000, and quarterly with more frequent deposits above $25,000. Quarterly Form M-941 returns are due the last day of the month after each quarter. Employees get W-2s by January 31 (February 1 in 2027); confirm the separate state reconciliation deadline with your payroll provider.
Paid Family and Medical Leave. PFML contributions and wage reports are filed quarterly through MassTaxConnect, due the last day of the month after each quarter. For 2027 the total contribution rate stays at 0.88 percent of eligible wages, but it is restructured: the family leave portion is 0.70 percent, with at least 60 percent paid by the employer, and the medical leave portion is 0.18 percent, which can be fully deducted from employees. Employers with fewer than 25 covered individuals do not pay the employer share, for an effective rate of 0.46 percent. The count of covered individuals can include 1099 contractors in some cases, which matters for startups that rely heavily on contractors. Update your payroll settings for the new split before your first 2027 payroll.
Unemployment insurance. Quarterly contribution reports with the Department of Unemployment Assistance follow the same April 30, July 31, October 31, and January 31 pattern.
Boston Personal Property: The Form of List
The City of Boston's Assessing Department requires businesses that own taxable personal property on January 1 to file State Tax Form 2, the Form of List, by March 1. Filing is electronic unless you show a hardship. If you do not file, the assessor estimates your property from comparable businesses, and the city can audit and assess unreported property for up to three years and six months.
For a C-corp, the actual tax is often zero or near zero: Massachusetts law exempts most personal property of business corporations from local tax because that value is captured in the corporate excise, and Boston has a small account exemption for personal property under $10,000 of assessed value. Unincorporated businesses, including LLCs taxed as partnerships, are generally taxable on furniture, fixtures, and equipment. If Boston sends you a Form of List, respond by March 1 rather than assuming the exemption covers you; the filing is what establishes it.
The 4 Percent Surtax: A Founder Exit Issue
Massachusetts taxes most income at a flat 5 percent, but since 2023 it has imposed an additional 4 percent surtax on taxable income above an indexed threshold. For tax year 2026 the threshold is $1,107,750, up from $1,083,150 in 2025; the 2027 figure will be published separately.
The surtax applies to total taxable income, including long-term capital gains. A founder who lives in Massachusetts and sells $10 million of stock in an acquisition faces roughly 9 percent state tax on most of that gain instead of 5 percent, or close to $356,000 of additional tax compared with the pre-2023 rules. Massachusetts also does not follow the federal QSBS exclusion the same way, so federally excluded gain may still be taxable in the state.
The planning levers are about timing and structure, and they have to be set up before the deal closes: spreading gain across tax years through installment terms or earnouts, charitable planning, and reviewing residency facts well in advance. A move out of state announced the week before closing rarely survives scrutiny. If an exit is plausible in the next two years, raise the surtax with your tax advisor now.
Federal and Delaware Dates in Brief
- February 1, 2027: W-2s and 1099-NEC for 2026, moved from Sunday January 31. For payments made after December 31, 2025, the One Big Beautiful Bill Act raised the federal 1099-NEC and 1099-MISC reporting threshold from $600 to $2,000, indexed for inflation starting in 2027. State information return requirements and thresholds are separate questions, so confirm what Massachusetts expects rather than assuming it follows the federal change.
- March 1, 2027: Delaware franchise tax and annual report. The minimum is $175 under the authorized shares method or $400 under the assumed par value capital method, plus the $50 annual report fee. Run both methods with our Delaware franchise tax calculator before you pay an inflated bill.
- April 15, 2027: Form 1120 or Form 7004, plus the first federal estimate.
- October 15, 2027: Extended Form 1120.
The Classic Boston Founder Mistakes
- Extending Form 355 without paying the $456. The extension is void without the minimum payment, so late penalties run from April 15.
- Assuming SaaS is not taxed. In Massachusetts it generally is, and a company with an office in Cambridge or the Seaport has nexus from its first sale.
- Filing sales tax quarterly after you crossed the monthly line. At $1,200 of annual tax, monthly filing applies.
- Running last year's PFML settings into 2027. The total rate is the same, but the employer and employee split changes.
- Skipping the annual report. It is due March 15, separate from any tax return.
- Ignoring the surtax until the term sheet. By the time an acquisition LOI is signed, most of the useful planning options are gone.
The Bottom Line for Early Stage Boston Startups
For a pre-revenue Delaware C-corp with a small Boston team, the core 2027 obligations are: a Certificate of Registration and annual report with the Secretary of the Commonwealth, Form 355 with the $456 minimum, quarterly M-941, PFML, and UI filings, a Form of List if the Assessing Department asks or you hold taxable property, and sales tax registration once you sell software into the state.
Use our tax compliance checklist tool to confirm which of these apply. StartupCFO tracks deadlines across all 50 states on every plan, and our tax service includes a 50 percent discount on preparation of one federal and one state return, with additional states and filing fees as add-ons. Book a free consultation and we will map your Massachusetts footprint.
This article is general information, not tax advice. Rates, thresholds, and deadlines change, and Massachusetts agencies and the City of Boston publish the controlling figures. Confirm your specific obligations with your CPA and the official pages at mass.gov/dor, sec.state.ma.us, and boston.gov before filing.
