LegalBench.PT: A Benchmark for Portuguese Law

Beatriz Canaverde, Telmo Pires, Andre Martins


Abstract
The growing use of LLMs in the legal field has spurred the creation of benchmarks across various jurisdictions and languages, yet none specifically focused on the Portuguese legal system. We present LegalBench.PT, the first comprehensive benchmark for Portuguese law. To develop it, we first collect long-form questions and answers from real law exams, and then use GPT-4o to convert them into multiple-choice, true/false, and matching formats. Once generated, the questions are filtered and processed to improve the quality of the dataset. To ensure accuracy and relevance, we validate our approach by having a legal professional review a sample of the generated questions. Although synthetically generated, we show that their basis in human-created exams and our rigorous filtering and processing methods applied result in a reliable benchmark for assessing LLMs’ legal knowledge and reasoning abilities. Finally, we evaluate the performance of leading LLMs on LegalBench.PT and investigate potential biases in GPT-4o’s responses. We also assess the performance of Portuguese lawyers on a sample of questions to establish a baseline for model comparison and validate the benchmark.
Anthology ID:
2026.nllp-1.30
Volume:
Proceedings of the Natural Legal Language Processing Workshop 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Nikolaos Aletras, Ilias Chalkidis, Leslie Barrett, Cătălina Goanță, Daniel Preoțiuc-Pietro, Gerasimos Spanakis, Shanshan Xu
Venues:
NLLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
334–349
Language:
URL:
https://aclanthology.org/2026.nllp-1.30/
DOI:
Bibkey:
Cite (ACL):
Beatriz Canaverde, Telmo Pires, and Andre Martins. 2026. LegalBench.PT: A Benchmark for Portuguese Law. In Proceedings of the Natural Legal Language Processing Workshop 2026, pages 334–349, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
LegalBench.PT: A Benchmark for Portuguese Law (Canaverde et al., NLLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.nllp-1.30.pdf