Peter Barr's contribution to national business was to establish accountancy as a profession. His career started when he joined R H Leary's Dunedin accounting and auctioneering business. He became junior partner in 1886 and principal after Leary's death in 1895.
Under Barr's direction the firm became a leading provider of professional services, developing into the national practice, Barr Burgess & Stewart.
Barr retired in 1934, having established himself as the father of accountancy by virtue of being a founding member of the Incorporated Institute of Accountants in New Zealand, its inaugural president and first president of its successor, the New Zealand Society of Accountants. Through his efforts, professional, university-standard education became mandatory for accountants.