Harvey Co-Builds Custom Model for Tax with PwC

This post details the co-development of the Tax AI Assistant with PwC, a custom model and LLM system for tax professionals. It highlights the process of combining curated tax datasets (legislation, case law, revenue guidance, PwC tax materials) with Harvey's LLM expertise and fine-tuning with feedback from PwC tax experts across 10+ jurisdictions. The system uses in-house models and semantic search, further tuned on tax datasets and expert-annotated examples. A key aspect is the human-guided approach, incorporating expert responses and guidance to optimize the dataset and model, followed by a feedback loop with engineers and tax experts to improve output quality. The post also presents results from a blind side-by-side human preference evaluation where the Tax AI Assistant was preferred 91% of the time by experts.