When a fiduciary duty is imposed, equity requires a different, arguably stricter, standard of behavior than the comparable tortious duty of care at common law.  It is said the fiduciary has a duty not to be in a situation where personal interests and fiduciary duty conflict, a duty not to be in a situation where his fiduciary duty conflicts with another fiduciary duty, and a duty not to profit from his fiduciary position without knowledge and consent. A fiduciary ideally would not have a conflict of interest.

Relationships

The most common circumstance where a fiduciary duty will arise is between a trustee, whether real or juristic, and a beneficiary. The trustee to whom property is legally committed is the legal—i.e., common law—owner of all such property. The beneficiary, at law, has no legal title to the trust; however, the trustee is bound by equity to suppress his own interests and administer the property only for the benefit of the beneficiary. In this way, the beneficiary obtains the use of property without being its technical owner.

Others, such as corporate directors, may be held to a fiduciary duty similar in some respects to that of a trustee. This happens when, for example, the directors of a bank are trustees for the depositors, the directors of a corporation are trustees for the stockholders or a guardian is trustee of his ward's property.  A person in a sensitive position sometimes protects himself from possible conflict of interest charges by setting up a blind trust, placing his financial affairs in the hands of a fiduciary and giving up all right to know about or intervene in their handling.

When a court desires to hold the offending party to a transaction responsible so as to prevent unjust enrichment, the judge can declare that a fiduciary relation exists between the parties, as though the offender were in fact a trustee for the partner.

Roman and civil law recognized a type of contract called fiducia (also contractus fiduciae or fiduciary contract), involving essentially a sale to a person coupled with an agreement that the purchaser should sell the property back upon the fulfillment of certain conditions. Such contracts were used in the emancipation of children, in connection with testamentary gifts and in pledges. Under Roman law a woman could arrange a fictitious sale called a fiduciary coemption in order to change her guardian or gain legal capacity to make a will.

Fiduciary principles may be applied in a variety of legal contexts.

Elements of duty

A fiduciary, such as the administrator, executor or guardian of an estate, may be legally required to file with a probate court or judge a surety bond, called a fiduciary bond or probate bond, to guarantee faithful performance of his duties. One of those duties may be to prepare, generally under oath, an inventory of the tangible or intangible property of the estate, describing the items or classes of property and usually placing a valuation on them.

A bank or other fiduciary having legal title to a mortgage may sell fractional shares to investors, thereby creating a participating mortgage.

Accountability

A fiduciary will be liable to account if proven to have acquired a profit, benefit or gain from the relationship by one of three mean^]

• In circumstances of conflict of duty and interest
• In circumstances of conflict of duty to one person and duty to another person
• By taking advantage of the fiduciary position.

Therefore, it is said the fiduciary has a duty not to be in a situation where personal interests and fiduciary duty conflict, a duty not to be in a situation where his fiduciary duty conflicts with another fiduciary duty, and not to profit from his fiduciary position without express knowledge and consent. A fiduciary cannot have a conflict of interest.

Conflict of duties

A fiduciary's duty must not conflict with another fiduciary duty. Stewart v Layton (1992) 111 ALR 687 Conflicts between one fiduciary duty and another fiduciary duty arise most often when a lawyer or an agent, such as a real estate agent, represent more than one client, and the interests of those clients conflict. This would occur when a lawyer attempts to represent both the plaintiff and the defendant in the same matter, for example. The rule comes from the logical conclusion that a fiduciary cannot make the principal's interests a top priority if he has two principals and their interests are diametrically opposed; he must balance the interests, which is not acceptable to equity. Therefore, the conflict of duty and duty rule is really an extension of the conflict of interest and duty rules.

No-profit rule

A fiduciary must not profit from the fiduciary position. This includes any benefits or profits which, although unrelated to the fiduciary position, came about because of an opportunity that the fiduciary position afforded. It is unnecessary that the principal would have been unable to make the profit; if the fiduciary makes a profit, by virtue of his role as fiduciary for the principal, then the fiduciary must report the profit to the principal. If the principal consents then the fiduciary may keep the benefit. If this requirement is not met then the property is deemed by the court to be held by the fiduciary on constructive trust for the principal.

Secret commissions, or bribes, also come under the no profit rule. The bribe shall be held in constructive trust for the principal. The person who made the bribe cannot recover it, since he has committed a crime. Similarly, the fiduciary, who received the bribe, has committed a crime. Fiduciary duties are an aspect of equity and, in accordance with the equitable principles, or maxims, equity serves those with clean hands. Therefore, the bribe is held on constructive trust for the principal, the only innocent party.

Bribes were initially considered not to be held on constructive trust, but were considered to be held as a debt by the fiduciary to the principal. This approach has been overruled; the bribe is now classified as a constructive trust. The change is due to pragmatic reasons, especially in regard to a bankrupt fiduciary. If a fiduciary takes a bribe and that bribe is considered a debt then if the fiduciary goes bankrupt the debt will be left in his pool of assets to be paid to creditors and the principal may miss out on recovery because other creditors were more secured. If the bribe is treated as held on a constructive trust then it will remain in the possession of the fiduciary, despite bankruptcy, until such time as the principal recovers it.

Breaches of duty and remedies

Conduct by a fiduciary may be deemed constructive fraud when it is based on acts, omissions or concealments considered fraudulent and that gives one an advantage against the other because such conduct—though not actually fraudulent, dishonest or deceitful—demands redress for reasons of public policy. Breach of fiduciary duty may occur in insider trading, when an insider or a related party makes trades in a corporation's securities based on material non-public information obtained during the performance of the insider's duties at the corporation. Breach of fiduciary duty by a lawyer with regard to a client, if negligent, may be a form of legal malpractice; if intentional, it may be remedied in equity.

Where a principal can establish both a fiduciary duty and a breach of that duty, through violation of the above rules, the court will find that the benefit gained by the fiduciary should be returned to the principal because it would be unconscionable to allow the fiduciary to retain the benefit by employing his strict common law legal rights. This will be the case, unless the fiduciary can show there was full disclosure of the conflict of interest or profit and that the principal fully accepted and freely consented to the fiduciary's course of action.

Remedies will differ according to the type of damage or benefit. They are usually distinguished between proprietary remedies, dealing with property, and personal remedies, dealing with pecuniary (monetary) compensation.

Compensatory damages

Compensatory damages are also available. Accounts of profits can be hard remedies to establish, therefore, a plaintiff will often seek compensation (damages) instead. Courts of equity initially had no power to award compensatory damages, which traditionally were a remedy at common law, but legislation and case law has changed the situation so compensatory damages may now be awarded for a purely equitable action.