In a business context, a breach of fiduciary duty occurs when an individual who is legally obligated to act in the best interests of another party violates that trust through misconduct or negligence. Under California law, a breach can be either intentional or negligent and typically involves a failure to uphold the core duties of loyalty, care, and full disclosure.

Specific actions that qualify as a breach include:

• Self-dealing: This occurs when a fiduciary personally gains at the expense of the beneficiary or the business entity.
• Misappropriation of corporate opportunities: This involves a director or officer diverting business opportunities away from the company for their own benefit.
• Conflicts of interest: Failing to disclose personal interests in transactions that affect the business is a frequent basis for litigation.
• Secret competition: This includes partners or officers secretly competing with the business or partnership.
• Fiduciary negligence: A breach can also occur if a fiduciary fails to exercise reasonable prudence or the required standard of care in their decision-making.
• Unauthorized transactions: Engaging in business deals or financial movements without proper authorization, such as a trustee performing unauthorized transactions.

To successfully prove a claim in California, a plaintiff must demonstrate the existence of a fiduciary relationship, a specific act of breach, and that the breach was a substantial factor in causing quantifiable financial damages.