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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, Managing Partner

(303) 692-8333

Boris Sobolev, CPA/CFF/CGMA, CVA, Partner joined Cornerstone in 2005 and became a partner in 2010. Boris was named one of National Association of Certified Analyst's (NACVA) 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. In 2017, Boris became Certified in Financial Forensics (CFF).

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.

Michael Schlueter, CPA/ABV/CFF, MBA, Partner

(303) 692-8333

Mike began his career in public accounting in 1999. Born and raised in Omaha, Nebraska, he earned a BSBA degree in Accounting and Business Finance and an MBA degree from the University of Nebraska at Omaha. Mike joined Cornerstone CPA Group in 2011 upon moving to Denver and became Partner in 2018.

Mike’s professional experience has focused on federal and state income taxes, financial statement compilation and review, and business valuation and financial forensics. In addition to his work experience, Mike has expert testimony experience in matters of valuation and forensic analysis.

Mike presently lives south of Denver with his wife, Amy, and their two children Emme and Eli. In his free, he enjoys spending time with his family, traveling, and following his favorite college football team, the Nebraska Cornhuskers.

In addition to being a Certified Public Accountant (CPA), Mike also holds the Accredited in Business Valuation (ABV) and Certified in Financial Forensics (CFF) credentials from the American Institute of Certified Public Accountants (AICPA).

Certified Public Accountant, Colorado Certificate 29639, Nebraska Certificate 6848 (Inactive).

Steven J Renhowe, M.T., CPA, CVA


Steven J. Renhowe, M.T., CPA has seven years of experience in public accounting, including both audit and tax experience. He earned a bachelor’s degree in business administration (with a double major in finance and accounting) from the University of Northern Colorado, and a master’s degree in taxation from the University of Denver. His public accounting experience has focused on corporate, partnership, and multi-state taxation, as well as income tax provisions for both public and private companies.

Steve was born in North Dakota, grew up in Fort Collins, and currently lives just south of Denver. His personal interests include reading, golfing, rooting for the Colorado Rockies, Denver Broncos, and Colorado Avalanche, as well as competing each year in a fantasy football league with friends from college. He also enjoys volunteering and hopes to travel more in the future.

Certified Public Accountant, Colorado Certificate number 26567

Kenneth R Naes, CPA


Ken joined the firm in early 2018. Prior to joining the firm Ken had spent the majority of his career working with large multi-national financial services firms such as AEGON, Transamerica and Jackson National Life Insurance Company.

Ken graduated from Rockhurst University with a Bachelor of Science in Business Administration in accounting. Ken has extensive finance, accounting and business development expertise. Ken’s analytical and problem solving skills make him an excellent forensic accountant.

Ken enjoys spending time outdoors with his wife Susan and his two sons.

Certified Public Accountant, Colorado Certificate number 9035857

Jonathan Weinstein CPA/ABV


Jonathan Weinstein, CPA/ABV joined the firm in early 2021. Prior to joining the firm, Jonathan worked for several firms around the New York City area. His career has focused on business valuations and forensic accounting, serving business owners operating in a variety of industries across the country in matters of gift and estate taxes, divorce, and equity-based compensation.

Jonathan graduated from Hofstra University with a Bachelor of Science in accounting. Jonathan acquired his CPA initially in September of 2015 in the State of New York and subsequently obtained his ABV credentials in November of 2019. In May of 2021, he obtained his reciprocal license in the State of Colorado.

Jonathan’s hobbies include cooking, hiking, mountain biking, and swing dancing.

Certified Public Accountant, Colorado Certificate number 9038081

Julie Barrett, Office Administrator


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 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, Hayley graduated from Regis University (2019), from the Nursing Program. She is now a Registered Nurse with a BSN,RNC. Her son, Logan, is graduating from college in the fall, and is Double Majoring in Criminal Justice and Sociology.

In her free time, which is not very often, she enjoys spending leisure time with her family and playing with her grandpuppies. Her daughter recently reminded her that she has an empty nest. She is currently seeking hobbies to fill that void. She is an avid Bronco fan and loves watching football.

Brian Campbell, Partner Emeritus


Brian Campbell, Partner Emeritus, 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.