Cohan rule is a former rule applicable in tax law. According to this rule, a taxpayer may approximate travel and entertainment expenses when no records exist, provided the taxpayer has taken all possible steps to provide documentation. The standard was set in the case Cohan v. Commissioner, 39 F.2d 540 (2d Cir. 1930) where the court held that the tax court may make a reasonable estimate of the allowable deduction, "bearing heavily if it chooses upon the taxpayer whose inexactitude is of his own making." The Cohan rule has been superseded by section 274(d) of the Internal Revenue Code, which now governs the deductibility of entertainment and travel expenses. Since 1962, travel and entertainment expenses have been only partly deductible and must be carefully documented.