Ask how many US businesses use AI and you get three defensible answers: 18 percent, 46 percent, and 77 percent. All three come from 2026 publications. None of them is wrong. The spread is a measurement artifact, and understanding why it exists is more useful than picking a favorite number, because the gap between the low figure and the high one is exactly the gap between using a tool and rebuilding a process around it.
Here is what the primary sources actually report, with the caveats that matter.
The government baseline
The US Census Bureau runs the Business Trends and Outlook Survey across roughly 1.2 million firms, which makes it the only probability sample at national scale. In its America Counts analysis published May 26, 2026, covering responses from December 14, 2025 through May 3, 2026, Census reported that AI use among US firms “hovered between 17% and 20%,” standing at 19.8 percent as of the period ending May 3, 2026, with 20 to 23 percent expecting to use it within six months.
The sector spread in that release: Information at 39.7 percent, Finance and Insurance at 33.9 percent, and Retail Trade at roughly 14 percent.
Size is the sharper divide. Census found 37 percent of firms with 250 or more employees using AI, and 32 percent of firms with 100 to 249 employees, against less than 20 percent of firms with four or fewer employees. Use rose among firms with 20 or more employees over the period and did not rise significantly among smaller ones.
The accounting sector figure
Census does not break out accounting in that release. It does in a working paper. Census Bureau CES Working Paper CES-26-25, “The Microstructure of AI Diffusion” (Bonney, Breaux, Dinlersoz, Foster, Haltiwanger and Pande, April 2026), drawing on the second BTOS AI supplement covering November 2025 through January 2026, puts Professional, Scientific, and Technical Services at 34 percent current AI use and 37 percent expected. That sector contains accounting firms, and it ranks second of all sectors, behind Information at 38 percent and ahead of Finance and Insurance at 30 percent. The national figure in that same supplement was 18 percent.
The Federal Reserve Board corroborates it independently. A FEDS Note by Jeffrey S. Allen published April 3, 2026, titled “Monitoring AI Adoption in the US Economy,” states that professional, scientific, and technical services and the financial sectors “stand out in terms of levels of adoption, at about 33 and 30 percent.”
Two numbers from the same paper are worth holding onto. The working paper found that 57 percent of adopters use AI in three or fewer business functions, with sales and marketing at 52 percent, strategy and business development at 45 percent, and IT at 41 percent. And 66 percent of firms use AI solely to augment tasks, with AI-related employment decreases reported at only 2 percent of firms.
The small business figure, and why it is higher
The Federal Reserve Banks‘ 2026 Report on Employer Firms, from the 2025 Small Business Credit Survey fielded September 3 through November 14, 2025 across 6,525 firms with one to 499 employees, found that 46 percent of firms reported that their business or its employees currently use AI, with an additional 15 percent planning to begin within twelve months and about a third having no plans.
Then it asked about depth, and the picture changes. Roughly half of users described themselves as experimenting. Forty four percent said partially integrated. Just 7 percent said fully integrated.
Task distribution ran to writing or marketing at 83 percent, individual productivity at 61 percent, and planning or analysis at 51 percent. On outcomes, 71 percent reported increased productivity, 39 percent improved quality, and 31 percent higher sales, with the vast majority reporting no change in labor costs. The most cited challenge among users was accuracy, at 46 percent.
The vendor figure, and its own footnote
Intuit QuickBooks‘ 2026 AI Impact Report, based on a survey of more than 34,000 small business owners plus anonymized data from over 5.3 million QuickBooks businesses across the US, Canada, UK and Australia, working with University of Chicago economists, reports that as of January 2026 77 percent of US businesses use AI regularly, up from 48 percent in July 2024. Seventy eight percent said AI improved productivity, up from 46 percent in July 2024, and 43 percent said it increased revenue against 2 percent who said it decreased.
Intuit’s own report contains the number that reconciles the gap. Looking at observed payment records rather than survey responses, only 12 percent of US businesses paid for dedicated AI tools between 2021 and 2025. The 77 percent figure explicitly includes free tools and features built into software people already use.
That is the whole methodological story. Census asks about AI use in producing goods or services and samples the business population. The Fed surveys small employers who opted in. Intuit surveys its own customer base and counts embedded features. Different frames, different wording, different answers, same underlying reality.
Professional services specifically
Thomson Reuters Institute‘s 2026 AI in Professional Services Report found organization-wide AI usage “almost doubled in the past year to 40% in 2026, compared to 22% in 2025,” with only 18 percent of respondents saying their organization tracks the return on investment of its AI tools and 15 percent reporting adoption of agentic AI. Its Future of Professionals 2026 report, covering more than 1,800 professionals across 62 countries, found 74 percent using AI tools several times a week and 44 percent multiple times a day. Both studies span legal, tax, accounting and risk, and both are global, so neither is a clean read on US accounting firms.
On readiness, a Fall 2025 survey of 1,735 executives across eight industries and eight geographies conducted by AICPA & CIMA with the NC State ERM Initiative, released February 25, 2026, found only 24 to 27 percent reporting adequate AI-skilled talent, IT system readiness, or regulatory preparedness, and that fewer than one in five smaller organizations had the required talent or systems. That is a cross-industry executive survey, not a survey of accounting firms, despite the publisher.
What it adds up to
Set the Census figure of 34 percent for the sector containing accounting against the Fed’s 7 percent fully integrated. A third of the sector is touching this. A small fraction has rebuilt anything around it. The SBA Office of Advocacy‘s 2025 Small Business Profiles counts 36.2 million US small businesses accounting for almost 46 percent of private sector employment, so the absolute numbers behind those percentages are large either way.
Adoption in accounting software has followed the same shallow pattern, arriving as features inside tools firms already run rather than as separate purchases. ConnectBooks, which syncs Amazon, Shopify, Walmart, TikTok Shop and eBay into QuickBooks and Xero for multi-marketplace sellers, has its AI layer Crunch in active beta, which is roughly where this category sits generally.
One figure deserves a warning. A claim that 73 percent of accounting firms have implemented AI automation, often cited as a 340 percent increase since 2022, circulates widely and does not appear on the AICPA page it is attributed to. The actual 73 percent in that release refers to early adopters who say AI provides strategic advantage. Check the source before repeating it.