Tax Services
Portland, OR
Located in South Portland, Withum is a leading Portland CPA firm focused on accounting, tax and advisory services.
As a top 25 national firm, Withum’s dedicated team members serve organizations across industries that range from startups to global enterprises. We are a technology-driven firm helping the Portland community grow and thrive with services ranging from cybersecurity and forensics accounting to employee benefit plan audits and outsourced accounting services…plus a whole suite of advisory solutions that will level up your success. That’s the Power in the Plus!
(818) 789 1179
Portland Service Specializations
Assurance and Accounting
Cybersecurity
Forensic and Valuation Services
State and Local Tax
Outsourced Accounting Systems and Services (OASyS)
Oregon State and Local Tax Updates
Do you or your organization operate in multiple states? Do you own property in a variety of states? Oregon State and Local Tax (SALT) laws are always changing and understanding the nuances of the states that you own or operate in is challenging. In these Oregon resources, you’ll find just a dash of the most up-to-date details on rules and regulations as state and local tax changes happen by state!
Industries We Focus on in Portland
Beyond the Region
- Inside Public Accounting Top 100 Firms – 23rd Largest Nationally
- Accounting Today Top 100 Firms – 22nd Largest Nationally
- Great Place to Work® – Fortune Best Workplaces for Parents and Women
- Vault Top 25 Accounting Firm
Partner In Charge
Joseph M. Thiermann, CPAJoe is a partner with over 25 years of specialized audit experience with audits of defined contribution plans, defined benefit plans, health and welfare plans, labor organizations and not-for-profits. He conducts system-wide reviews, designs and implements accounting systems and works on special projects involving system design, expense reporting and compliance, often in conjunction with other professionals to resolve regulatory and general management issues for clients.
Joe is an avid public speaker, having presented at the Annual Conference of the International Foundation of Employee Benefit Plans (IFEBP), the IFEBP Accountants’ Institute and the Oregon Labor Law Conference, and even taught business courses to contractors.
Portland Leadership
Withum in the News
INSIDE Public Accounting Names Withum to 2026 Best of the Best List
This accolade reflects the Firm’s long-term growth strategy centered on world-class client service, investment in innovation and strategic expansion. Ranking as a top-20 firm, Withum was recognized in the Best of the Best category for firms with more than $10 million in net revenue, earning a place among the profession’s top-performing accounting and advisory firms….
Buffalo Business First Names Christine Stolzenburg to 40 Under 40 Class of 2026
A decade after being recognized as a Buffalo Business First 30 Under 30 honoree, Christine’s selection highlights the continued growth of her influence as a leader, advisor and advocate for the Western New York community. Professional Experience and Industry Focus As a principal with more than 15 years of public accounting experience, Christine provides audit…
Construction Executive Names Withum Among Top 50 Construction Accounting Firms
This recognition reflects Withum’s deep specialization and longstanding commitment to the industry, with the Firm ranking among the top 20 construction accounting firms since 2019. For more than five decades, Withum has advised contractors, developers, suppliers, manufacturers, landscapers, dealers, renewable energy companies and other organizations across the construction ecosystem. The Firm’s Construction Services Team helps…
NJBIZ Names James Trubenbach-Byrne to 2026 People to Watch in Finance List
As a partner and leader within the Firm’s Healthcare and Not-For-Profit Services Teams, James serves healthcare organizations, not-for-profit entities, educational institutions and recipients of governmental funding. He specializes in providing audit services to complex healthcare and nonprofit organizations, helping leadership teams strengthen internal controls, improve operational efficiency and make informed business decisions. James works closely…
Withum Leaders Named as Global Top 200 Cannabis Accountants for 2026
The recognition reflects Withum’s commitment to serving cannabis businesses through specialized tax, audit and advisory services. These professionals represent the depth and breadth of Withum’s Cannabis Services Team, working with cultivators, manufacturers, dispensaries, multi-state operators and ancillary businesses. The Cannabis Services Team helps clients navigate tax regulations, financial reporting requirements and business challenges in a…
Contact Us
We will make every attempt to respond to your inquiry in a timely manner.