The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. (March 2018) (Learn how and when to remove this template message)
In contract law, the implied covenant of good faith and fair dealing is a general presumption that the parties to a contract will deal with each other honestly, fairly, and in good faith, so as to not destroy the right of the other party or parties to receive the benefits of the contract. It is implied in a number of contract types in order to reinforce the express covenants or promises of the contract. A lawsuit (or a cause of action) based upon the breach of the covenant may arise when one party to the contract attempts to claim the benefit of a technical excuse for breaching the contract, or when he or she uses specific contractual terms in isolation in order to refuse to perform his or her contractual obligations, despite the general circumstances and understandings between the parties. When a court or trier of fact interprets a contract, there is always an "implied covenant of good faith and fair dealing" in every written agreement.
In U.S. law, the legal concept of implied covenant of good faith and fair dealing arose in the mid-19th century because contemporary legal interpretations of “the express contract language, interpreted strictly, appeared to grant unbridled discretion to one of the parties”. In 1933, in the case of Kirke La Shelle Company v. The Paul Armstrong Company et al. 263 N.Y. 79; 188 N.E. 163; 1933 N.Y., the New York Court of Appeals said:
In every contract there is an implied covenant that neither party shall do anything, which will have the effect of destroying or injuring the right of the other party, to receive the fruits of the contract. In other words, every contract has an implied covenant of good faith and fair dealing.
Furthermore, the covenant was discussed in the First Restatement of Contracts by the American Law Institute, but before adoption of the Uniform Commercial Code in the 1950s, the common law of most states did not recognize an implied covenant of good faith and fair dealing in contracts.. Certain states, such as Massachusetts, have stricter enforcement than others. For example, the Commonwealth of Massachusetts will assess punitive damages under Chapter 93A which governs Unfair and Deceptive Business Practices, and a party found to have violated the covenant of good faith and fair dealing under 93A may be liable for punitive damages, legal fees and treble damages. 
In criminal law
In the Indian Penal Code, "good faith" is defined under Section 52 as Nothing is said to be done or believed in "good faith" which is done or believed without due care and attention.  The Privy Council expanded on this meaning in the case of Muhammad Ishaq v. The Emperor (1914), in which it held that an action taken by the defendant based on a belief of having a decree passed in his favour, was illegal since he could have found out that he in fact did not enjoy any such favourable decree, if he had inquired with a little more care and attention.
Contemporary usage in the USA
The implied covenant of good faith and fair dealing is especially important in U.S. law. It was incorporated into the Uniform Commercial Code (as part of Section 1-304), and was codified by the American Law Institute as Section 205 of the Restatement (Second) of Contracts.
Most U.S. jurisdictions view the breach of the implied covenant of good faith and fair dealing solely as a variant of breach of contract, in which the implied covenant is merely a "gap-filler" that provides yet another contractual term, and breach thereof simply gives rise to ordinary contractual damages. Of course, this is not the most ideal rule for plaintiffs, since consequential damages for breach of contract are subject to certain limitations (see Hadley v. Baxendale).
In certain jurisdictions, breach of the implied covenant can also give rise to a tort action, e.g. A.C. Shaw Construction v. Washoe County, 105 Nevada 913, 915, 784 P.2d 9, 10 (1989). This rule is most prevalent in insurance law, when the insurer's breach of the implied covenant may give rise to a tort action known as insurance bad faith. The advantage of tort liability is that it supports broader compensatory damages as well as the possibility of punitive damages.
Some plaintiffs have attempted to persuade courts to extend tort liability for breach of the implied covenant from insurers to other powerful defendants like employers and banks. However, most U.S. courts have followed the example of certain landmark decisions from California courts, which rejected such tort liability against employers in 1988[better source needed] and against banks in 1989.[better source needed]
Contemporary usage in Canada
Contemporary usage in Europe
The English private law has traditionally been averse to general clauses and has repeatedly rejected the adoption of good faith as a core concept of private law. Over the past thirty years, EU law has injected the notion of "good faith" into confined areas of English private law. The majority of these EU interventions have concerned the protection of consumers in their interactions with businesses. Only Directive 86/653/EEC on the co-ordination of the laws of the Member States relating to self-employed commercial agents has brought "good faith" to English commercial law.
On the European Continent, Good Faith often is strongly rooted in the legal framework. In the German speaking area, "Treu und Glauben" (Good faith) has a firm legal value, e.g. in Switzerland, where the Constitution's Art. 5 states that the state and private actors have to act in good faith. This leads to the assumption, e.g. in contracts, that all parties have signed in good faith and any missing or unclear aspect of a contract shall be interpreted based on the assumption of good faith of all parties.
In Australian General Insurance
The concept of 'good faith' was established in the Insurance industry following the events of Carter v Boehm  3 Burr 1905 and is enshrined in Australian Legislation, The Insurance Contracts Act 1984 (ICA). The Act stipulates under Section 13 the obligations of all parties within the contract to act with utmost good faith.
- Dubroff, Harold (2006). "The Implied Covenant of Good Faith in Contract Interpretation and Gap-Filling: Reviling a Revered Relic". St. John's Law Review. 80 (2): 559–619.
- "Section 52 of the Indian Penal Code". Central Government Act. Retrieved 8 March 2018 – via Indian Kanoon.
- Piggott (2 April 1914). "Muhammad Ishaq vs Emperor". indiankanoon.org. Allahabad High Court. Retrieved 8 March 2018.
- See A.C. Shaw Construction v. Washoe County, 105 Nev. 913, 915, 784 P.2d 9, 10 (1989).
- Foley v. Interactive Data Corp., 47 Cal. 3d 654, 665 (1988).
- Price v. Wells Fargo Bank, 213 Cal. App. 3d 465 (1989).
- https://scc-csc.lexum.com/scc-csc/scc-csc/en/item/14438/index.do SCC 71
- Zimmermann, Reinhard; Whittaker, Simon (2000-06-08). Good Faith in European Contract Law. Cambridge University Press. ISBN 9780521771900.
- Brownsword, Roger; Hird, Norma J.; Howells, Geraint G. (1999). Good Faith in Contract: Concept and Context. Ashgate/Dartmouth. ISBN 9781855219250.
- "EU Consumer Law and Policy". www.e-elgar.com. Retrieved 2017-06-16.
- Tosato, Andrea (2016-09-01). "Commercial Agency and the Duty to Act in Good Faith" (PDF). Oxford Journal of Legal Studies. 36 (3): 661–695. doi:10.1093/ojls/gqv040. ISSN 0143-6503.
- "Wikipedia (German), Artikel zu "Treu_und_Glauben"". Retrieved 2019-03-31.
- "Schweizerische Bundesverfassung vom 18. April 1999, Art. 5". Retrieved 2019-03-31.
- "Carter v Boehm", Wikipedia, 2019-04-13, retrieved 2019-08-07
- Treasury. "Insurance Contracts Act 1984". www.legislation.gov.au. Retrieved 2019-08-07.