A unilateral error occurs when only one contracting party is wrong about the terms or objects contained in a contract.  This type of error is more common than other types of errors. [ref. needed] The first step is to distinguish between mechanical calculations and commercial errors when considering one-sided errors. [ref. needed] In most cases, an error of law is not accepted as grounds for cancelling a contract. Proving that an innocent party has been misled in the contracting process can be difficult and rarely stands up in court. If only one of the parties is wrong, that party has no right to withdraw unless (1) the non-erroneous party knew of the error and it was his fault that caused the error, or (2) the effect of the error is such that the application of the Contract would be “unscrupulous”. See Larsen v. Johannes (1970) 7 Cal. App.3d 491 503; Rest. 2d, Contracts §153(a).
The Error Registration and Correction Act was raised by the United States Court of International Trade in Hynix Semiconductor America, Inc. v. United States, 414 F. Supp. 2d 1317 (T.C.C. 2006), where the Court was confronted with the application of a tariff calculated by a customs officer at the erroneous rate. In order to enforce “anti-dumping” legislation against foreign-produced products (in this case, Korean electronic components) that were produced with cheap labor and were inferior to those of the US industry, a regulatory system was introduced under which such imports were subject to a “liquidation duty” at a rate that can be found in a schedule. The schedule was established by a panel of experts who used standards to adjust the price difference for foreign goods. The customs officer used the wrong class of goods and overcharged duties, and when Hynix discovered what had happened, part of a very short limitation period had expired.
However, Hynix won the case and obtained the correction of its duty rate by proving that such an error.” could be corrected under 19 U.S.C. § 1520(c) as an error of fact or clerical error that does not constitute an error of interpretation of any law, and because failure to object within ninety days of the liquidation of registrations has no legal consequence in this regard. Id. at page 1319. A common mistake is like a mutual mistake because both sides are wrong. What distinguishes a common mistake is that it is the fault of both parties. There are three types of errors in contract law: unilateral errors, mutual errors and common errors. An example of a legal error would be a criminal who enters into a contract because a senior official gave him false information about the law.
If the criminal realizes his mistake, he can cancel the contract due to a legal error. Illustration: Lady found a stone and sold it as topaz for $1 ($25 today). It was an uncut rough diamond worth $700 ($17,000 today). The contract is not cancellable. There was no mistake, because neither party knew what the stone was.  Here, a legal defense error could help Jack successfully challenge the conspiracy charge. Jack honestly believed he had permission to sell marijuana according to the law. Therefore, he did not intend to violate a drug law and did not have the mindset to “conspire “. He simply made a mistake in good faith in interpreting a state law. An example of a common mistake would be when two parties enter into a contract in which one person agrees to carry goods for the other person at a certain cost. Later, both sides might find that the price of gas was higher than what both had negotiated, which increased transportation costs. They could make a common mistake and renegotiate the contract with the new gas prices.
Error of law: If a party enters into a contract without knowing the law of the country, the contract is affected by these errors, but it is not void. The reason is that ignorance of the law is no excuse. However, if a party is led to conclude an agreement by an error of law, such a contract is not valid.  Factual errors can apply to a wide range of offences. Some crimes may show that a factual error is a defence.