Groundbreaking Study: AI Outperforms Humans in Legal Invoice Review – A Wake-Up Call for Law Firms

by | Aug 22, 2025 | Legal AI News | 0 comments

Onit's AI Center for Excellence Releases In-Depth Study of AI for Legal Invoice Analysis

A transformative study, “Better Bill GPT: Comparing Large Language Models against Legal Invoice Reviewers,” recently published on arXiv, showcases the unparalleled potential of AI in reshaping legal operations. Conducted by Onit Inc., this research pits advanced Large Language Models (LLMs) like GPT-4o and Gemini against human reviewers—early-career lawyers, experienced lawyers, and legal operations professionals—in the critical task of legal invoice review. The findings are striking: LLMs achieved up to 92% accuracy in invoice approval decisions, surpassing the 72% ceiling set by experienced lawyers, while reducing review times from minutes to as little as 3.6 seconds and cutting costs by 99.97%—from $4.27 per invoice for humans to mere cents for legal AI.

The study highlights AI’s superiority in granular tasks, such as line-item classification, where LLMs scored F-scores up to 81%, compared to just 43% for the best human group. By identifying non-compliant items like block billing or unauthorized tasks with precision, AI for legal analysis delivers significant value through enhanced compliance and dramatic cost savings. This efficiency allows legal teams to shift focus from tedious manual reviews to high-value strategic work, fundamentally transforming legal spend management.

An Android and a paralegal, both reviewing invoices.

Building on our insights from “The Legal Playbook is Being Rewritten, and the Revolution has Just Begun,” where we discussed the broader AI-driven shift in the legal sector, this study provides concrete evidence of AI’s disruptive power. At Adjuria, we specialize in AI-centric consulting and tech solutions for law firms, leveraging intelligent agents to automate document processing and workflows, such as invoice management and contract analysis. Our tailored solutions empower firms to integrate LLMs seamlessly, ensuring compliance and boosting operational efficiency.

Adjuria’s consulting services go beyond implementation, offering customized intelligent agents that streamline repetitive tasks like invoice review, document drafting, and workflow automation. These ai agents learn from your firm’s unique processes, reducing errors and accelerating decision-making while maintaining ethical standards. For lawyers and support staff considering AI adoption, the study underscores a critical reality: firms without a robust AI strategy risk losing their competitive edge in an industry where speed, accuracy, and cost-efficiency are paramount.

The era of AI-powered legal operations is here, and law firms must act swiftly to stay ahead. Adjuria’s expertise in deploying intelligent agents can transform your legal workflows, future-proof your operations, and position your firm as a leader in this AI revolution. Contact us today to discover how our ai tools for legal workflows can elevate your legal practice.

#AIinLaw #LegalTech #FutureOfLaw #ArtificialIntelligence #LegalConsulting #Adjuria #OnitStudy #AIRevolution

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Written By Daniel Henson

Social Media Coordinator, Adjuria, LLC

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