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About Us


For years, Cornerstone CPA Group has been providing quality, personalized financial guidance to local individuals and businesses. Cornerstone CPA Group's expertise ranges from basic tax management and accounting services to more in-depth services such as audits, financial statements, and financial planning.

Cornerstone CPA Group is one of the leading firms in and throughout Denver. By combining our expertise, experience and the team mentality of our staff, we assure that every client receives the close analysis and attention they deserve. Our dedication to high standards, hiring of seasoned tax professionals, and work ethic is the reason our client base returns year after year.

Firm License #6760

Our Mission

Our mission is to help clients maintain financial viability in the present, while taking a proactive approach to achieve future goals. This requires open communication to reach an understanding of our clients' needs through research and sound analysis. Cornerstone CPA Group is dedicated to meeting these goals with high standards of excellence and professionalism. We have been a staple of Denver's business community for years, and pride ourselves on the level of esteem we have earned.

Our dedication to hard work has earned the respect of the business and financial community in and around Denver. We believe this to be a direct derivative of our talent and responsiveness to our client base. Whether you are a current or prospective client, rest assured that individuals and businesses who choose Cornerstone CPA Group receive competent and timely advice.

Our Team

Boris V. Sobolev, CPA/CFF/CGMA, CVA, Partner (303) 692-8333 ext. 215

Boris Sobolev, CPA/CFF/CGMA, CVA, Partner joined Cornerstone in 2005 and became a partner in 2010. Boris was named one of NACVA's 40 under 40 in 2017. This is a prestigious award recognizing the accomplishments of outstanding individuals in business. His passion lies in working with small to medium-size businesses whether it is helping with accounting, consulting, tax compliance or valuation. Our clients appreciate Boris's diligence, professionalism and his unrelenting attention to their needs.

Boris has testified in many District Courts along the Front Range and the Mountains. Boris has played a leading role in performing extensive forensic and tracing analyses as well as complex business valuations. This has earned him recognition among some of the leading attorneys in Denver.

Boris graduated UCLA with honors with a major in Economics and a minor in accounting in 2002. In 2003, he became one of the youngest individuals to pass all four parts of the CPA exam in the country. In 2005, he obtained a Certified Valuation Analyst license (CVA), giving him foundation in business valuation, litigation support and forensic analysis.

Boris moved to the United States from Russia with his family in 1994. Boris and his wife Margarita enjoy spending time outdoors and travelling with their two young sons. In the past, Boris co-founded Resource Stock Guide website and continues to be an active investor today.

Certified Public Accountant, Colorado Certificate number 23810, Firm Responsible Party.

Brian Campbell, CPA, ABV, Partner (303) 692-8333 ext. 216

Brian Campbell, CPA, ABV started his accounting career in 1971 as the Deputy County Treasurer & Deputy County Clerk for Jefferson County, Colorado. While working in Jeffco, he passed his CPA examination. Upon leaving the County in 1975, he began his public accounting career with Thomas A. Ward & Co, a local Denver CPA firm and qualified for his CPA License in 1976.

Brian left Thomas A Ward & Co in 1985 to form his own Firm. In 1988 he established a partnership with Allan S. Rosenbaum. In 1994, David Irvine joined to form Campbell Irvine & Rosenbaum, PC. In 1999, Rosenbaum withdrew and the Firm, Cornerstone CPA Group, PC was established. Boris Sobolev joined as an equal partner in 2010

His employment history is as follows: Cornerstone CPA Group, PC 1999-Present (Principal) Campbell, Irvine & Rosenbaum, PC 1994-1999 (Shareholder/President) Campbell & Rosenbaum 1988-1994 (Partner) Brian Campbell 1985-1988 (Sole Proprietor) Thomas A. Ward & Co. 1979-1985 (Shareholder) 1975-1979 (Firm Member) Jefferson County Colorado 1971-1975 (Deputy County Treasurer & Clerk)

Brian is almost a native of Colorado having moved to Denver in 1956. He graduated from Lakewood High School and then from the University of Colorado in 1967 earning a degree in Finance and Accounting. He is an active member of the AICPA, CSCPA and in 2004 obtained his ABV Certificate (Accredited Business Valuator). This advanced his longtime passion for Business Valuation and Litigation Support. Brian has valued numerous businesses and testified in substantially all of the Colorado Judicial Districts since commencing his valuation/litigation specialty over 30 years ago. He has thoroughly enjoyed his participation in the accounting profession.

In his spare time, he enjoys hiking, biking, skiing and tending to his back yard pond. Any opportunity to spend time with his wife and ten grandchildren (all of whom live in Colorado) is a joy. He likes staying fit and has participated in the San Francisco and New York Marathons as well as bicycle tours in Italy and France. Occasionally, he has also been known to spend an afternoon or evening at Coors field watching a Rockies game. For each of the last 23 years, he has taken an annual ski trip with three high school classmates. Every year is a new destination including breathtaking Vancouver, BC, the Swiss Alps, and Italy.

Certified Public Accountant, Colorado Certificate number 3837

David C. Irvine, MBA, CGMA, Partner (303) 692-8333 ext. 217

Dave Irvine, MBA, CGMA has practiced public accounting since 1966 with two years taken for graduate school at the University of Southern California. His career has been focused on working with closely held business owners that request advice in income tax matters and financial management, but also advice on time tested principles of sound business ethics, risk management and ownership succession.

Dave has always been active in community organizations. He was a charter member of the Denver Cherry Creek Rotary Club, President and Chairman of the Board of the National Kidney Foundation and an officer and director of The Colorado Society of Certified Public Accountants.

Dave has three grown children, four grandchildren and lives in the heart of downtown Denver with Kathy, his wife of 41 years. He is an active skier, bike rider and a motorcycle enthusiast.

Certified Public Accountant, Colorado Certificate number 2268.

Michael Schlueter, CPA/ABV/CFF, MBA, Manager (303) 692-8333 ext. 222

Mike Schlueter, CPA/ABV/CFF, MBA, Manager, has over 17 years of experience in public accounting. He earned a BS/BA degree in Accounting and Business Finance and an MBA degree from the University of Nebraska at Omaha. His professional interest areas include: personal and business taxation, financial reporting, and business valuation.

Mike relocated to Colorado in 2011 with his family and joined Cornerstone the same year. He has since become a key person in dealing with complex tax issues and litigation support matters.

Mike presently lives just south of Denver with his wife, Amy, and their two children Emme and Eli. His passions include his family, outdoor activities and college football (especially the Nebraska Cornhuskers).

Certified Public Accountant, Colorado Certificate number 29639.

Theavy Sok, MACC, MsIT, Associate (303) 692-8333 ext. 223

Theavy Sok, MACC, MsIT - is a Cambodian immigrant. She joined the firm in early 2010. Shortly after joining the firm, she assumed a key role in the firm’s Quality Control Process utilizing her years of experience in process mapping, documentation, and internal auditing.

Theavy excels in the preparation of compiled and reviewed financial statements. She also provides financial analysis and operational review services to clients. She is passionate about assisting entrepreneurs with improving and understanding the importance of their accounting information system in managing their businesses. Theavy is a strong and fast self-learner. She has become the firms’ consultant on payroll, accounting services, QuickBooks accounting and assistance, and financial data extraction and conversion.

While finishing her master degree of Accountancy at Daniels Business College at the University of Denver, she was employed at a Large Telecommunication company as a Staff Auditor III and became a Senior Staff Auditor the following year. She conducted Sarbanes Oxley Testing, fraud and operating audits, and she implemented process improvements.

She is an avid gardener especially for high country and xeriscape gardening. She used to operate a 50 hive apiary served on an organic berry farm located in Brighton.

Julie Barrett, Office Administrator 303-692-8333 ext 210

Julie has been with the firm since August 2001. Her role in the firm is Office Administrator. She is responsible for much of the administrative work in the office. She is the first point of contact when a client or business associate calls our firm. She often responds to specific client needs and also maintains accounting records and performs payroll functions for some of our clients. Her outgoing and gregarious attitude helps maintain a pleasant atmosphere within the office and is enjoyed by our clientele.

Julie is a Colorado native and grew up in the suburbs of Denver. She is married to a chef; and no, her husband does not cook (much) at home. Her daughter attends Regis University, and is in the Nursing program, graduating in the Spring of 2019. Her son is a senior at Green Mountain High School and a National Honor Society student. He just completed the Youth Police Academy in Golden, where he is interning. He will be graduating high school this year, and attending the University of Wyoming in the fall to study Criminal Justice and Fish and Wildlife Management.

Julie is a consummate mother. There is no limit to the support and guidance she provides to her children. In her free time, which is limited with the young adults, she enjoys spending leisure time with her family. She has been known to catch a fish or two and enjoys being outside in the mountains. She is an avid Bronco fan and loves watching football.