Castro & Co Anniversary

We Are Castro & Company 

An innovative, reliable, and accomplished CPA firm

Who We Serve

Proudly Working with the Federal Government for over 20 years, including the following Departments and Agencies:

Castro Ampersand
Thomas and Millie

Our Story

For over two decades, Castro & Company has solidified its position as a leading audit, advisory, and accounting firm in the heart of the Washington, DC, Metro area.

We serve as hands-on, trustworthy advisors to our clients with a methodology grounded in customized and innovative services. Our team’s work commemorates our country’s proud traditions; indeed, our track record demonstrates initiative, expertise, and outstanding results.

Primary NAICS Codes:

Auditing: 541211
Advisory: 541611
Accounting: 541219

Our Values

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Castro & Company consists of passionate and seasoned professionals who approach each client’s needs with a proactive mindset. Every team member commits to going above and beyond in delivering outstanding services. 

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We believe compelling results are only possible through the latest industry procedures. Therefore, our ability to adapt to this versatile industry illustrates our commitment to excellence.

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Our unwavering dedication to client needs and mission requirements has established our reputation as a reliable strategic partner. We share considerable trust and confidence with our clients because we prioritize their satisfaction.

Our Memberships & Affiliations 


Member of the AICPA GAQC

Castro & Company is a proud member of the AICPA Government Audit Quality Center (GAQC), demonstrating our commitment to delivering high-quality services. We are also a licensed CPA firm in Virginia and the District of Columbia.

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AGA Corporate Member

As a Corporate Partner, Castro & Company gains exclusive access to senior professionals and opportunities to promote excellent government management practices through research and publications.

Our Team

Thomas Castro

Thomas Castro, CPA

Founder & Managing Partner

Mr. Thomas Castro has over 25 years of experience in public accounting with extensive experience providing Federal Government audit, advisory, & accounting services.

Millie Seijo

Millie Seijo, CPA


Ms. Millie Seijo has over 25 years of experience in public accounting, with extensive experience providing Federal Government audit, advisory, & accounting services.

Wayne Ference

Wayne Ference, CPA


Mr. Wayne Ference has over 30 years of experience in public accounting, exclusively providing Federal Government audit, advisory, & accounting services.

Team members collaborating


A CPA firm is only as good as its people. We proudly cultivate an environment of collaboration, encouragement, and diversity. Those seeking a fulfilling, challenging, and rewarding career will find one at Castro & Company.

Industry Insights

Aug 01

In this age of rapid technological advancement, artificial intelligence has started to play a significant role in various fields including the realm of public accounting.

Apr 23

Imagine a workplace where it doesn’t matter the color of your skin, ethnicity, gender, age, culture, or physical limitations. A place where you’re celebrated for

Apr 22

NASA awarded contracts to six companies, including Castro & Company to provide agency-wide contract auditing support services.