Article 57 provides a straightforward but essential anti-avoidance rule: no expense or amount mentioned in the Law (specifically Articles 54 and 55) may be deducted more than once when determining taxable income for any tax year. This prevents taxpayers from claiming the same cost under multiple categories or in different years to artificially deflate their taxable profits. By explicitly prohibiting double deductions, the Law ensures that the tax base is protected from redundant accounting entries that would otherwise reduce the legitimate tax liability of the business.