Article 193 establishes the 'procedural vs. substantive' rule for the transition phase. New procedural rules (such as for audits, objections, and suits) apply immediately upon the Law taking effect. However, the determination of the actual tax, income, or loss for any historical tax year must follow the 'substantive' rules that were in force during that specific year. For cases currently under review, the new dispute procedures apply unless a decision or judgment was already pending. This ensures that taxpayers are assessed fairly based on past laws while benefiting from modern procedural rights and timelines.