Under Article 14, taxpayers are permitted to deduct bad debts that arise from the sale of goods or services. A primary condition for this deduction is that the income associated with the debt must have been previously declared as taxable income by the taxpayer. To claim the deduction, the bad debt must be formally written off from the taxpayer's financial books. Additionally, the taxpayer is required to furnish suitable evidence which proves that the debt is impossible to collect. The specific requirements for this evidence are further detailed in the implementing Regulations, ensuring only genuinely unrecoverable debts are deducted.