Peter Reading, who joined the firm in 2001 as a 21-year-old trainee, is now Partner in the firm’s Assurance and Advisory Group.
His focus will be on regulated audit work and compliance advice in the construction and real estate sector.
Mr Reading said: “I am delighted to have been made a partner at the firm I first joined as a trainee.
“I have been supported every step of the way during my career, and in my new role I look forward to providing further opportunities around helping clients succeed in their business aims.”
Sarah Fitzgerald has also joined MHA Carpenter Box at partner level with the firm’s Business Services Group.
She previously ran her own accountancy practice in West Sussex and brings more than 25 years’ experience to the firm.
The company says Ms Fitzgerald will also be “providing owner-managed businesses with expert advice covering strategic planning and business development, as well as providing expert tax and accounting support.”
She said: “I am thrilled to be joining the leadership team of such a forward-thinking firm of accountants.
“MHA Carpenter Box enjoys a great reputation across the region reflecting its progressive values and the importance it places on client relationships.”
In addition to the new partners, MHA Carpenter Box has also appointed two new directors to its leadership team.
James Gawman has been promoted from associate within the Assurance and Advisory Group to compliance director, while Rachel Pearce has been promoted from associate to client service director in the company’s Tax Services Group.