O’Brien & Co. Boston · CPAs Book a consultation
Boston, Massachusetts · Est. 2009

Business tax, accounting & advisory.

O’Brien & Co. is a mid-sized regional CPA firm serving privately held businesses across New England. We carry the compliance calendar that keeps you current, and do the planning that changes the number at the bottom.

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AICPA member firm · Massachusetts Society of CPAs · Peer reviewed
Business Tax Compliance, planning, credits, controversy Accounting Close, assurance, CFO support, payroll Advisory Valuation, transactions, succession 14 All services
Professional services Construction & real estate Life sciences & technology Healthcare practices Manufacturing & distribution Nonprofits Restaurants & hospitality Family offices
What we do

Three practice areas that
rarely stay in their lane.

A tax question is usually an accounting question wearing a different hat, and an advisory question is both of them looking three years out. Our teams sit together so the answer arrives whole rather than in pieces.

Business Tax

Federal, state and local compliance handled on a calendar you can see, and a planning conversation that starts in the spring, not the week before an extension runs out. Entity choice, multi-state nexus, credits, and representation when a notice arrives.

  • Corporate, partnership and S-corp returns
  • Multi-state nexus and apportionment studies
  • R&D credits and Massachusetts incentives
  • IRS and DOR examination representation
Business tax

Accounting

A close that lands on the same day every month, statements your lender accepts without a second draft, and a controller-level review before the numbers leave the building.

  • Outsourced accounting and month-end close
  • Audits, reviews and compilations
  • Fractional controller and CFO support
  • Payroll and contractor compliance
Accounting services

Advisory

The decisions that only come around once, such as a sale, a buy-in or a generational handoff, supported by people who already know how the books were built.

  • Business valuation and fairness opinions
  • Buy- and sell-side transaction advisory
  • Succession and exit planning
  • Entity structuring and private client tax
Advisory services
Full directory

Fourteen specializations,
each with its own page.

Every practice area breaks into the specific work behind it: what it covers, who it’s for, what you receive, and how the engagement runs. No mystery scope, no discovery call required to find out what we actually do.

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17
Years serving New England businesses
240+
Privately held companies on retainer
10th
Of the month your books are closed
21
States we file in each year
How we work

A year that runs on
a schedule, not a scramble.

Most firms show up in March. We build the year backwards from your filing deadlines so that by the time the returns are due, there is nothing left to discover.

01

Diagnostic

Two weeks, fixed fee.

We read three years of returns and the current trial balance before we quote anything. You get a written summary of what looks right, what looks exposed, and what we would change, whether or not you engage us.

02

Engagement design

Scope, fee and calendar in writing.

Every deliverable gets a name, an owner and a date. Fees are quoted annually, not hourly, so a question in July doesn’t arrive as a line item in August.

03

The working year

Monthly close, quarterly review.

Books close by the tenth. A partner reviews the quarter with you before estimates go out, which is when planning still changes the outcome instead of merely explaining it.

04

Filing & forward look

No surprises in April.

Returns are drafted from numbers you have already seen. The closing meeting is about next year: structure, credits, distributions and the things worth moving before December.

Elaine E. O'Brien, CPA, CMA, Managing Partner of O'Brien & Co.
Elaine E. O’Brien, CPA, CMA Managing Partner
Leadership
“A client should never learn something about their own company from us in April. If we’ve done the year properly, the return is a formality.”

Elaine E. O’Brien, CPA, CMA has led the firm since 2022, bringing fifteen years of corporate finance leadership: CFO strategy, M&A due diligence and GAAP compliance. She reviews every valuation and transaction engagement that leaves the office, and still carries a small portfolio of owner-managed clients herself.

Elaine’s profile About the firm
Insights

Written for owners,
not for other accountants.

Short notes on the rules that actually move money in a private company, published when something changes, not on a content calendar.

All insights
Tax June 2026

Section 174 and the software company that never wrote software

Capitalization rules catch more companies than the name suggests. A short test for whether yours is one of them.

6 min read
Multi-state May 2026

Remote employees created a nexus problem. Here is the cheapest way out.

One salesperson in a new state can trigger registration, payroll and income tax filings. Voluntary disclosure usually beats waiting.

5 min read
Advisory April 2026

What a buyer’s quality of earnings report will find in your books

The five adjustments that come up in nearly every lower-middle-market deal, and how to settle them before diligence starts.

8 min read
Next step

Start with the diagnostic.
Decide about us after.

Two weeks, a fixed fee, and a written read on your last three years, yours to keep whichever way you go.

Book a consultation (617) 555-0142