How to Create Custom AI Tax Website for any specific country

I’m working on creating a website that provides AI-driven answers and calculations related to Specific Country tax laws. My goal is to build a system that can accurately respond to tax-related queries and perform complex calculations based on a large dataset of tax information. What would be the most efficient way to develop such a website? I have tried fine tuning gpt with 500+ prompts related to tax rules, tax related practice questions and their answrs but it did not even gave the response which was included in jsonl file. it was very dissapointing for me. Can you please tell me write way to create custom ai tax website.