Article 48 outlines the documentary evidence required for a Taxable Person to exercise their right to deduct input tax. To claim a deduction, the person must possess a valid Tax Invoice issued in accordance with the Agreement's provisions. For imported goods, customs documents proving the import was conducted under the GCC Common Customs Law are mandatory. The article provides flexibility, allowing individual Member States to permit tax deductions even without a compliant Tax Invoice. This is permissible provided the Taxable Person can establish the value of the tax due through alternative, verifiable means.