OpenAI and Thrive Holdings have jointly developed an AI-powered tax preparation system called Tax AI, which was recently tested across Crete’s network of over 30 accounting firms during the U.S. tax filing season.
The platform was designed to assist accountants by automating tasks such as extracting information from documents, mapping fields, and preparing parts of tax returns, while still keeping human professionals involved in the final review and approval process.
According to OpenAI, the system helped reduce the amount of time spent on tax preparation by nearly one-third and boosted overall productivity by around 50%.
Instead of acting as a fully autonomous tax filing tool, Tax AI works as a controlled automation system where accountants remain responsible for reviewing completed returns. Cases that involve uncertainty or errors are redirected to engineering and product teams for further improvements.
The technology was built using OpenAI’s Codex model and relies on a continuous self-improvement process. Corrections made by accountants are collected as structured feedback, recurring issues are transformed into evaluation datasets, and Codex is then used to identify problems, suggest fixes, and test updates before they are rolled out.
OpenAI stated that Tax AI can draft tax returns with up to 97% accuracy, although the company mainly measures performance through correct field completion rates rather than one overall accuracy score.
During the initial rollout, only about 25% of tax returns achieved at least 75% correct field completion before human review. However, within six weeks, that number increased to 86%. The company also revealed that close to 60% of returns were at least 90% complete before manual corrections, while approximately 9.5% required no field-level edits at all.
At first, the system focused mainly on simpler W-2 and 1099 tax filing workflows. Over time, it expanded to handle more advanced filings involving K-1 forms, rental property schedules, and tasks requiring reconciliation across multiple documents.
Beyond tax preparation, OpenAI and Thrive believe the project demonstrates how “self-improving AI agents” can continuously learn from real-world feedback through structured evaluation systems and AI-assisted software development.
The companies are now exploring the same framework for additional business functions, including bookkeeping, auditing, and operational processes such as IT help desk support.
The rollout is part of a wider partnership announced earlier this year, in which OpenAI acquired an equity stake in Thrive Holdings as part of efforts to modernise industries that still depend heavily on outdated operational systems.
