How are different accounting firms using AI in 2025?

TL;DR: Thomson Reuters’ 2025 Generative AI in Professional Services Report reveals 21% of tax firms currently use GenAI, with 53% planning adoption or considering it. The Big 4 accounting firms—Deloitte, EY, PwC, and KPMG—lead with custom AI platforms for audit automation and client solutions, whilst smaller firms focus on tax research, return preparation, and advisory services using AI-powered tools.

Shifting perspective: From scepticism to excitement

Artificial intelligence has transitioned from optional technology to essential infrastructure in accounting, with firm owners fundamentally shifting their perspective. The 2025 Generative AI in Professional Services Report from Thomson Reuters Institute found that 68% of tax and accounting professionals are excited and/or hopeful about GenAI’s future in the industry.

“Current and emerging generations of GenAI tools could be transformative,” said one US director of tax. “For example, deep research capabilities, software application development, and using GenAI to help with business storytelling would have significant impacts on the future of professional work.”

Adoption accelerates across firm sizes

According to survey respondents, 21% of tax firms identified as already using GenAI technology, with 53% either planning to use the technology or considering it. Only a quarter of firms (25%) still have no current plans to use GenAI—down dramatically from 49% in 2024, indicating rapid industry transformation.

Among firms actively using or planning to use GenAI, 44% reported using the technology daily, if not multiple times per day, with an additional 29% using it weekly. This frequency demonstrates that GenAI has moved beyond experimental pilots to operational integration.

Open-source versus industry-specific tools

Interestingly, accountants appear to be implementing GenAI primarily through personal, open-source tools rather than industry-specific platforms. Amongst tax firm survey respondents already using GenAI tools, 52% are using open-source technology such as ChatGPT, whilst only 17% are using industry-specific tools.

This trend could shift as more industry-specific technology providers introduce their own GenAI solutions in coming years, potentially offering greater integration with existing accounting workflows and compliance requirements.

How the Big 4 use artificial intelligence

The Big 4 accounting firms—Deloitte, Ernst & Young (EY), PwC, and KPMG—have led AI adoption with substantial investments in AI-powered tools and solutions:

Deloitte: Audit document review

Deloitte has developed GenAI and agentic capabilities in its audit platform. The AI-powered tool can perform initial reviews of audit documentation and suggest enhancements for clarity and consistency, accelerating the audit review process whilst maintaining quality standards.

EY: Unifying technology stack

In 2023, EY launched an AI platform combining leading EY technology platforms with AI capabilities across strategy, transactions, transformation, risk, insurance, and tax. EY recently announced new AI capabilities supporting the organisation’s 160,000+ global audit engagements, representing enterprise-scale AI deployment.

PwC: IT development and audit automation

In-house teams at PwC have developed customised software applications for employees that synthesise data, complete and review code, conduct granular troubleshooting, and more. They have observed 20% to 50% productivity gains in development processes through GenAI. Additionally, PwC estimates that a new end-to-end AI-driven audit solution will be complete in 2026.

KPMG: Trusted AI framework

KPMG’s Trusted AI framework helps member firms’ clients design, build, deploy, and use AI technology solutions in a responsible and ethical manner, building loyalty and partnerships whilst addressing governance concerns that remain barriers to AI adoption.

How smaller accounting firms use AI

Smaller accounting firms, whilst lacking the resources of the Big 4, are embracing AI to remain competitive and offer enhanced services. The 2025 GenAI report identified the top five use cases for tax firms using or planning to use GenAI:

1. Tax research

Firms use AI-powered algorithms in tax research tools to return data from human-edited, tax-specific content. This provides authoritative answers from trusted sources quickly and accurately, dramatically reducing research time compared to manual methods.

2. Tax return preparation

Firms are using AI to automate the extraction and analysis of data from various financial documents, significantly reducing the time and effort required to prepare accurate tax returns. GenAI assists in identifying applicable deductions and credits tailored to individual or corporate financial scenarios, ensuring compliance and optimisation of tax liabilities.

3. Tax advisory

Firms are using AI tools to generate predictive insights, helping clients plan for future tax implications based on their financial decisions. This provides a more strategic role for tax professionals, allowing them to offer value-added services beyond compliance work.

4. Accounting and bookkeeping automation

Firms are using AI-powered software to automatically categorise expenses, reconcile accounts, and generate financial reports. This saves time and reduces the risk of manual errors, enabling staff to focus on higher-value analytical work.

5. Document summarisation

Firms use AI to summarise key points from contracts, invoices, and receipts and can quickly identify anomalies requiring further investigation. This capability speeds up the review process whilst enhancing the accuracy and reliability of financial audits and compliance checks.

Daily integration becomes the norm

The frequency of AI usage amongst adopters demonstrates that the technology has moved beyond experimental status. With 44% of firms using GenAI daily or multiple times per day, and an additional 29% using it weekly, AI has become integrated into routine workflows rather than reserved for special projects.

This operational integration suggests that early concerns about AI accuracy, reliability, and professional judgement have been addressed through improved models, better training, and clearer guidelines for appropriate use cases.

Approaching AI with curiosity

Thomson Reuters positions AI not as a threat but as an opportunity for firms of all sizes to offer better services, improve efficiency, and thrive in an ever-changing industry. As AI continues to advance, those who approach it with curiosity and willingness to embrace new technology will likely stay ahead of industry trends.

The shift from 49% of firms having no AI plans in 2024 to only 25% in 2025 demonstrates that the accounting industry has crossed a critical adoption threshold. The question for firms is no longer whether to adopt AI, but how quickly they can integrate it effectively whilst maintaining professional standards and client trust.

Source: Thomson Reuters Tax & Accounting Original Article: How are different accounting firms using AI in 2025? Published: 4 November 2025