Company lists · Data refreshed September 2026

Top 25 Professional services firms based in Washington, United States

Name: Professional services firms based in Washington, United States
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Sep 5, 2026 138 companies tracked

RevenueBase identified 138 professional services firms headquartered in Washington, United States as of September 2026 and tracks 1,106 professional contacts across them, including 282 with verified work emails. New York is the largest hub.

This list covers professional services firms headquartered in Washington, United States, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Every row shows the company's own description, how directly it supports the match, and when it was last checked. Data refreshed September 5, 2026.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase SmartSearch, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.

How to read this list HQ checked on every row Match evidence on every row Refreshed Sep 5, 2026 86% judged on-target in blind review

138Companies

1,106Contacts tracked

282Verified emails

Explore all 138 companies → Free signup · no credit card · 500 free credits

The 25 largest professional services firms based in Washington, United States

Ranked by team size

Top 25 of 138 professional services firms based in Washington, United States, ranked by team size, largest first. Data refreshed Sep 5, 2026. Evidence rates how directly each company's own description names professional services firms: strong (names it), partial (names part of it), indirect (matched on its full profile rather than the summary shown). Click a count to unlock that company's people.
#	Company	Headquarters	Employees	Contacts
1	IBM PromontoryIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	501-1,000	403
	“IBM Promontory is a global leader in strategy, risk management, and compliance consulting.#IBMConsulting” Source: company website · checked Sep 5, 2026
2	Raffa, PCIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	1,001-5,000	87
	“Top accounting firm Raffa, P.C.” Source: company website · checked Sep 5, 2026
3	HAN Group LLCIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	51-200	51
	“Han Group is a public accounting firm committed to serving the nonprofit community by providing unparalleled expertise in nonprofit Audits & Assurance, Managed Accounting, Tax…” Source: company website · checked Sep 5, 2026
4	Iuvo SystemsIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	11-50	36
	“At Iuvo Systems Inc, we empower government contractors and federal agencies to succeed by delivering specialized accounting, compliance, and business solutions tailored to the…” Source: company website · checked Sep 5, 2026
5	Bazilio Cobb AssociatesStrong evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	201-500	28
	“Since our founding in 1983, Bazilio Cobb Associates has provided professional services to federal, state, and local government agencies; Fortune 500 companies; nonprofit…” Source: company website · checked Sep 5, 2026
6	IBS Management & Consultancy ServicesIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	51-200	21
	“IBS is an Accounting, Finance, Management, and Transaction Advisory consulting firm.” Source: company website · checked Sep 5, 2026
7	Quatt AssociatesIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	11-50	19
	“Quatt Associates, Inc.” Source: company website · checked Sep 5, 2026
8	Panda AccountingIndirect evidence	Washington, UT, United StatesHQ checked Sep 5, 2026	51-200	19
	Source: company website · checked Sep 5, 2026
9	Rosemckenna, PllcStrong evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	11-50	17
	“RoseMcKenna PLLC is a boutique accounting firm dedicated to providing the absolute best in personalized and professional tax services.” Source: company website · checked Sep 5, 2026
10	CWP Consulting INCStrong evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	11-50	16
	“CWP Consulting was built around the desire to provide quality, professional services to individuals and business owners through the use of specialized and individualized services.” Source: company website · checked Sep 5, 2026
11	The Kenrich Group LLCIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	51-200	14
	“The Kenrich Group, an HKA Company, is a business and litigation consulting firm with 50 offices in 19 countries.” Source: company website · checked Sep 5, 2026
12	CFO Services GroupIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	1-10	12
	“CFO Services Group is your dedicated accounting team and much more.” Source: company website · checked Sep 5, 2026
13	Seiler, Singleton & Associates, PAIndirect evidence	Washington, NC, United StatesHQ checked Sep 5, 2026	1-10	9
	“At Seiler, Singleton & Associates, P.A, our goal is to offer quality accounting, tax, payroll, and advisory services to individuals, small businesses, and nonprofit organizations.” Source: company website · checked Sep 5, 2026
14	Aa&t GroupIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	1-10	9
	“We provide value to our clients, empowering them to succeed.” Source: company website · checked Sep 5, 2026
15	Phillips, Salmi Associates, LLCIndirect evidence	Washington, IL, United StatesHQ checked Sep 5, 2026	1-10	8
	“Background Phillips, Salmi + Associates, LLC is a certified public accounting firm with locations in Washington and Springfield, Illinois.” Source: company website · checked Sep 5, 2026
16	O Riordan Bethel LAW Firm, LLPIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	11-50	7
	“Nationally-recognized and award-winning economists, lawyers and public policy experts providing public policy analysis; business process improvement; research and analysis…” Source: company website · checked Sep 5, 2026
17	Gray Global Advisors, LLCIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	1-10	7
	“Gray Global Advisors is a full-service advisory firm that provides innovative industry focused strategic development and implementation services.” Source: company website · checked Sep 5, 2026
18	Helfer And Company, LLCIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	1-10	7
	“For over three decades, Alan S.” Source: company website · checked Sep 5, 2026
19	Accounting 4 DCIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	1-10	7
	“At Accounting 4 DC, our goal is to help our clients run healthy, profitable businesses.” Source: company website · checked Sep 5, 2026
20	Leftwich LLCIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	11-50	7
	“Leftwich LLC is a multi-disciplinary legal and consulting firm.” Source: company website · checked Sep 5, 2026
21	Credibility International, An HKA CompanyStrong evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	11-50	6
	“Our professionals have focused our careers upon becoming functionally excellent in the fields of accounting and finance.” Source: company website · checked Sep 5, 2026
22	Allenmitchell, LLP Cpas & ConsultantsIndirect evidence	Washington, IA, United StatesHQ checked Sep 5, 2026	1-10	5
	“At AllenMitchell, our goal is to provide the top shelf service that you've come to expect at larger national and regional firms but in a more relaxed environment and at a price…” Source: company website · checked Sep 5, 2026
23	Morgan Wingate & Co, P.CIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	11-50	5
	“Welcome to the firm of” Source: company website · checked Sep 5, 2026
24	Franklin & TurnerStrong evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	51-200	5
	“Hamilton Enterprises, LLC, is an assurance and advisory company that provides professional services to clients.” Source: company website · checked Sep 5, 2026
25	ConsultvisoryIndirect evidence	Washington, DC, United StatesHQ checked Sep 5, 2026	11-50	5
	“At ConsultVisory, we specialize in navigating the intricate landscape of Regulatory Compliance, Finance & Accounting Services, Strategic Marketing, Information & Technology…” Source: company website · checked Sep 5, 2026

Showing 25 of 138 professional services firms based in Washington, United States

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Professional services firms based in Washington, United States at a glance

As of Sep 5, 2026

1-10Median size (employees)

New YorkLargest hub · 593 HQs

Contacts with mobile numbers

Sep 5, 2026Data refreshed

Companies by employee count

1-10

11-50

51-200

201-500

501-1,000

1,001-5,000

Email recency for this list is measured across the whole United States list rather than this city, so it is reported there. Company counts and contact totals on this page are exact for Washington, over 138 companies.

How this list was built

Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among professional services firms, so some rows will be adjacent to the category rather than pure plays. The description and evidence rating on every row are there so you can check each match yourself.

Source: The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase SmartSearch, the natural-language company search available to every RevenueBase user.
What qualifies: Companies headquartered in Washington, United States whose own description of what they do matches “professional services firms”. Matching reads each company's description, not its industry code or its name.
What we exclude: Companies whose own description does not clearly place them among professional services firms, and records with no verified work email. Companies headquartered outside Washington are excluded even when they keep an office there.
Match quality: In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and an evidence rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
Ranking: Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
Verification: Every listed company carries at least one verified work email, 282 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
Refresh: This page's figures were pulled from the company graph on September 5, 2026. Lists refresh periodically as the graph is re-checked.
Corrections: Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.

Professional services firms by metro in the United States

Frequently asked

How many professional services firms are there based in Washington, United States?

RevenueBase identified 138 professional services firms headquartered in Washington, United States as of September 2026, matched on each company's own description of what it does rather than its industry code.

What is the largest company on this list?

IBM Promontory, headquartered in Washington, tops this list with the largest team on record.

Which city has the most professional services firms?

New York leads with 593 headquartered companies, followed by Houston (420) and Atlanta (304).

How do I get contact information for these companies?

A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 282 verified decision-maker contacts tracked across these 138 companies.

How current is this list?

The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 5, 2026.

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About this data

RevenueBase is a B2B data infrastructure company. Its company graph covers 60 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph with RevenueBase SmartSearch, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.