Staff Profiles


David Simpson is a certified public accountant who has specialized in financial and tax planning for more than 35 years – always in the public accounting sector. David’s certifications and affiliations are numerous; beginning with his Bachelor of Science – Accounting emphasis from the University of Southern California, he has been a Certified Public Accountant in the state of California since 1983, a member of the American Institute of Certified Public Accountants (AICPA) and California Society of Certified Public accountants.

Owning his own Certified Public Accounting firm since 1986 was the natural progression for David after having spent six years with the “Big Eight” firm of Touche Ross (now known as Deloitte.) in both the auditing and tax departments. During those years David pursued a graduate degree Masters in Business Taxation from the University of Southern California which was completed in 1987.

Since owning his own firm, David has enjoyed the challenge of the field of taxation and directed the firm to specialize in business and individual tax planning and preparation. Whereas the firm also provides services in the areas of accounting and accounting software consulting the main emphasis has been in tax planning and preparation.

Outside of the office, David has pursued an interest in ice hockey into actually playing “fun” level hockey, coaching his daughter’s sports teams, traveling as much as time will permit and spending time with his family.

SHAY LEIMBACH | Accounting Manager


Ysabel joined the Simpson & Co. staff in June 2015. She was originally hired as an office manager while attending college. In 2018, she earned her Bachelor’s Degree in Accounting from California State University, Fullerton. After completing her undergraduate degree, she decided she wanted to continue to further her education and returned to her alma mater to attend graduate school. In 2022, she earned her Master’s degree in Taxation from California State University, Fullerton. Since 2018, Ysabel has significantly increased her responsibilities in the office and currently is a tax manager in the firm. Over the last four years, Ysabel’s responsibilities within the firm have increased to include correspondence with taxing authorities as needed, preparation of federal and state income tax projections and the preparation of individual, sales, payroll, and property tax returns. Also, she currently provides various accounting services for her business clients, both on-site and remotely. These accounting responsibilities include financial statement preparation, bank account reconciliations, and period ending adjusting journal entries. Ysabel is currently studying for the CPA exam with the goal of obtaining her CPA designation.

In her free time Ysabel enjoys traveling with her husband, taking pictures, going to concerts, and occasionally binge-watching TV shows. Her favorite TV show is HBO’s Game of Thrones (notwithstanding Season 8!).

JESSICA RAMOS | Administrative Assistant

If you have contacted Simpson & Co. you may have already met Jessica. Jessica is the most recent addition to the company starting in 2019 as an administrative assistant. Some of her daily duties include speaking to clients, scheduling appointments and mailing out tax returns. She completed her Associate’s in Accounting in 2019 and has plans to pursue a Master’s degree in Taxation from Cal State Fullerton.

In her free time Jessica enjoys watching the newest TV shows, going to restaurants, and playing board games.