Deploying LLM Agents for Auditable Complaint Investigation in Banking

John Hartley, Conor Brian Hamill, Azam Din, Fayz Siddiqui, Kingsley Nketia Acheampong, Greig A Cowan, Raad Khraishi


Abstract
Complaint investigation in retail banking requires handlers to synthesise evidence from heterogeneous enterprise systems into policy-aligned summaries. We present a production-deployed tool-augmented LLM agent at a major UK retail bank that assists this process under human review. Given a complaint record, the agent queries 16 typed, schema-validated tools and returns an investigation summary with a source-cited chronological evidence timeline. We evaluate the system using SME assessment, LLM-as-a-Judge monitoring, rework measurement, and downstream impact testing. On 187 paired complaints, SMEs judged the agent to match or exceed historical human-written production investigations in 90% of cases across faithfulness, relevance, completeness, and coherence. Median investigation time falls from 30 minutes to 23 seconds. Operational controls include daily automated monitoring, pre-defined thresholds, hallucination flagging, and periodic human audit. These results demonstrate that constrained single-agent LLMs with typed tools are viable for scalable, auditable complaint investigation in regulated environments.
Anthology ID:
2026.emnlp-industry.227
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Pepa Atanasova, Gholamreza Haffari, Minghan Wang
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
3802–3813
Language:
URL:
https://aclanthology.org/2026.emnlp-industry.227/
DOI:
Bibkey:
Cite (ACL):
John Hartley, Conor Brian Hamill, Azam Din, Fayz Siddiqui, Kingsley Nketia Acheampong, Greig A Cowan, and Raad Khraishi. 2026. Deploying LLM Agents for Auditable Complaint Investigation in Banking. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track, pages 3802–3813, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Deploying LLM Agents for Auditable Complaint Investigation in Banking (Hartley et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-industry.227.pdf