Our Team

Prewitt CPA, PLLC is a full-service Certified Public Accounting firm licensed in TX. All our CPA's hold valid TX State CPA Certificates.

Our Team:

John Mark Prewitt, CPA - Managing Member

In 2012, John Mark (JM) founded Prewitt CPA in order to serve small businesses' and individuals' tax needs. JM grew up in a family full of business owners, which instilled an entrepreneurial spirit and a passion for helping small businesses and individuals develop a better understanding of tax planning.


After graduating from Texas A&M University in College Station, Texas (BBA Accounting & MS Finance), JM began his accounting career with PwC and later his financial advisory business with Woodbury Financial.

In addition to being a CPA, he is currently securities licensed (Series 7 & 66). In 2016, JM also became a Founding Partner in Cohesion Wealth Advisors, a full service financial advisory firm, and in 2017 helped to found Cohesion Business Advisors, a full service consulting firm.


John Mark and his wife, Carleigh, currently reside in Dallas, TX. Outside of work, John Mark is an avid outdoorsman, Aggie football fan, and is an active member of the Touchdown Club of Dallas, Park Cities Quail, and Dallas Safari Club.

Brendan O'Connor, CPA -  Tax Manager

Brendan joined Prewitt CPA in June of 2020 and currently manages the tax practice. Brendan has 10+ years of experience working for various mid-sized public accounting firms and industry accounting roles. Brendan’s well-rounded accounting background and technical training has allowed him to gain an understanding of our clients’ needs and service them in a thoughtful and inquisitive manner.


Brendan attended University of Denver where he received a B.S. in Accounting from the Daniels School of Business and a Masters in Taxation from the Sturm College of Law. Brendan is a Texas Licensed CPA and has spent most of his career working for mid-sized accounting firms focusing on real estate, oil and gas, banking and high net worth individual tax clients. 


Brendan and his wife, Mallory currently reside in University Park, TX with their two kids. Outside of work Brendan enjoys spending time with his family, golfing, watching sports and brewing beer.

Marti Flores-Sierra - Office Director

Marti has 31 plus years of experience in the financial services industry. Over those 31 years, she has gained invaluable industry knowledge by working with an array of financial firms. She currently is a Registered Assistant with Cohesion Wealth Advisors, LLC (SCF Securities).

Marti is responsible for the team’s operational management and works closely with clients to provide a high level of service and effective solutions for all financial needs.


Marti is very involved in the community.  She is a member of Freedom Fellowship Int’l where she teaches children's church. She also has a ministry called Homeless of Dallas where you can find her, every Wednesday, feeding and clothing the homeless.


Marti resides in Waxahachie, Texas, with her husband Steve. She has 6 children, three whom still reside at home, and 4 grandchildren. When not tending to 4 dogs and a cat, you can find her watching her favorite teams, the Dallas Cowboys and the Texas Aggies.

Jonathan Freeman - Tax Associate

Jonathan Freeman joins us from the financial sector where he spent 15 years helping business owners fine tune their practices and growing stronger, more well-developed strategies for long term success. His ability to build relationships and all professionalism makes Jonathan a great fit to the team.

“The relationship and trust I’ve developed with clients over time is by far my greatest career achievement. I hope to bring a feeling of client focused enthusiasm to the already well-established team."


He is a graduate from the University of North Texas and is currently studying for his master’s degree at Texas A&M Commerce. His goal is to sit for the CPA exam after his studies and help further the growth of our clients and their businesses.


He is active in community, where he is on the Town Council and heavily involved in the youth sports programs.  He was born and raised in the Dallas area and has spent most of his life in Sunnyvale. Him and his wife Andrea, have 2 kids and enjoy time with their family.

Ken Herman -  Tax Associate

Growing up, Ken was surrounded by family operating in small businesses and the financial services industries which shaped his desire to help individuals and business owners in these areas. He enjoys most getting to know people to develop and generate awareness in the areas of tax and business planning. In addition to helping serve client needs, Ken shares in the day to day operations as well as the strategic planning & marketing for Prewitt CPA, PLLC.


After graduating from Texas A&M University, He began his career consulting with entities in the areas of budgeting, finance and operations. Ken is a seasoned and dedicated team leader with over twelve years of experience in the management and operations field. Additionally, Ken brings over ten years of extensive financial services knowledge to benefit all of our clients. Ken serves clients in the areas of tax, bookkeeping & payroll.


A native Texan, Ken grew up in Dallas near the White Rock Lake area. Volunteering in the local community has been a priority for Ken as he continues to serve on a leadership board for his Delta Tau Delta Fraternity. He is actively involved as a counselor at Lake Pointe Church - Firewheel for members and guests, and coordinates activities for the men of his life group.


Autumn is one of Ken's favorite times of year as he enjoys watching Aggie football, hunting & fishing. Ken and his wife, Kim, also enjoy spending time with their daughters Audrey & Alaina.

Chase Graham -  Tax Associate

Chase joined Prewitt CPA in June 2021 as a tax associate looking to work with clients to help meet their financial goals. He is looking to learn through experience while continuing to serve his client’s needs.


Chase graduated from Texas A&M University with a BBA Accounting.  


From Houston, Chase moved to Dallas following his graduation to join Prewitt CPA. In his free time he enjoys spending time with friends, traveling, and watching Aggie sports.

Brianna Hernandez - Administrative Assistant

Brianna Hernandez joins Prewitt CPA, PLLC having a knack for understanding and serving client needs who are seeking guidance in the accounting and financial industries.  Having the working knowledge of the firm's processes allows her the ability to welcome and serve your needs daily.


 She joined our team as a part time student at Strayer University, continuing her Bachelor's Degree in Business Administrative in order to provide a high level of client service, clear communication, and trusted guidance. Brianna is an integral part of the team helping clients understand QuickBooks and the pathway for their desired financial outcomes.


Brianna resides in Duncanville, Texas where she is a proud first-time homeowner.  When not working or studying, Brianna likes to travel, enjoys trying new foods and loves spending time with her significant other and their dog Tebow.

Taylor Lane Brown - Client Liaison

Taylor joined the team in November 2020 and currently serves as a client liaison for Prewitt CPA, PLLC and Cohesion Business Advisors, LLC.


She has 10 years of experience working in client focused roles, with a specialty in AP accounting and relationship management. Taylor has primarily worked in the energy industry, most notable leading the accounts payable team for a small oil and gas operator in Austin, Texas. She has also spent time working in private wealth management, assisting with client’s financial needs, and servicing their portfolios. Taylor’s attention to detail, mixed with her love of people and nurturing personality makes her a great fit for our client liaison role.  She graduated from Texas Christian University on the Dean’s Honor List, with a Bachelor of Science in Public Relations.


Taylor was born and raised in Dallas, TX and currently lives in the Preston Hollow area with her husband, Taylor. Outside of work Taylor enjoys traveling, hiking, yoga, participating in Dallas Junior Garden Club and spending time with her family and friends.

Get In Touch

At Prewitt CPA, PLLC, we've been serving the accounting needs of Dallas, TX and the surrounding areas for years. If you need help managing any aspect of your home or business's finances, we want to hear from you.

Please fill out this form and let us know how we can be of service. We happily offer initial consultations to determine how we can best serve you.

Thank you for visiting. We look forward to working together!

Prewitt CPA, PLLC

4245 N Central Expressway Suite 235
Dallas, TX 75205

T: 214.528.4511
F: 214.528.1793


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Securities offered through SCF Securities, Inc. • Member FINRA/SIPC • 155 E. Shaw Ave., Suite 102, Fresno, CA 93710 • 800.955.2517 • 559.456.6109 FAX. • Investment advisory services offered through SCF Investment Advisors Inc., SCF Securities, Inc., Cohesion Wealth Advisors, LLC, and Prewitt CPA, PLLC are independently owned and operated. • Securities offerings limited to residents of LA, OK, AR, TX CA, KS, ME. • Check the background of this investment professional on FINRA's BrokerCheck

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