The IRS Has No Rules for AI Tax Prep — And That's Your Firm's Problem, Not Theirs

Published: April 14, 2026 | By: The Crossing Report

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Summary

Basis AI has built an AI platform that completes a 1065 partnership return — start to finish, no human hands. It is deployed today at nearly a third of the top 25 US accounting firms. The IRS has issued zero guidance on how that should be disclosed to clients, what constitutes adequate review, or where liability sits if the AI makes an error. That combination — autonomous AI capability and a complete regulatory vacuum — is not an abstract future risk. It is the situation your firm may already be operating in. Here is what to do about it.

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Part 1: What Autonomous AI Tax Return Prep Actually Means Now

In February 2026, Basis AI announced it had completed an autonomous end-to-end 1065 partnership return — the most complex standard return type a small CPA firm regularly handles.

A 1065 is not a simple filing. It requires computing income allocations across multiple partners and their K-1s, managing special allocation elections, reconciling multi-entity structures, and handling the cascade effects that flow into each partner's individual return. Getting it wrong doesn't just affect one taxpayer — a K-1 allocation error can misstate the tax picture for every partner on the return.

Basis AI completed that return — document intake through finished product — without a human hand in the execution loop. The platform is already deployed at 30% of the top-25 US accounting firms and 20% of the top-150, with reported efficiency gains of 30–50% firm-wide.

It helps to understand the distinction from tools like Thomson Reuters Ready to Review, which gets standard 1040s 80–90% complete for a human to finalize. Ready to Review assists; a human CPA still drives the return to completion. Basis AI achieved autonomous completion of a harder return type. That is a materially different risk category — not because the AI is more dangerous, but because the human review role is different and the existing guidance wasn't written for it.

You may not be using Basis AI at your firm today. But your clients' returns may eventually flow through firms that do. And whether or not you're using it now, the regulatory vacuum that surrounds it applies to any AI-assisted return preparation your firm already does. This is the story that matters right now.

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Part 2: What Happens When No Rules Exist

As of April 2026, the IRS has issued no guidance on any of the following:

• Whether clients must be told that AI assisted in preparing their return
• What constitutes adequate human review of an AI-generated return
• Where professional liability sits if an AI-assisted return contains an error that a CPA signed off on
• Whether there is any safe harbor for firms that use autonomous AI tools in their workflow

Bloomberg Tax documented this gap explicitly: "IRS Standards on AI and Tax Preparation Would Protect Businesses." Morgan Lewis, writing in April 2026, noted that AI enforcement is accelerating broadly while federal policy continues to lag — with state attorneys general stepping in to fill the gap.

Consider the scenario this creates. An AI platform completes a 1065. A CPA does what they would characterize as a standard review and signs the return. The return is filed. Two years later, an audit surfaces a K-1 allocation error. The question now on the table: what was the CPA's review process? What did they check? What evidence exists that the review was substantive rather than a rubber stamp on an AI output?

If no written protocol exists, the answer to those questions is silence. Silence in a professional liability context is not neutral.

The absence of IRS guidance is, in a specific sense, worse than having bad guidance. Bad guidance at least tells you where the lines are. The current situation tells CPA firms that they are operating on professional judgment alone — in a technological environment that the existing professional standards weren't designed for.

That gap is yours to fill, not the IRS's. The IRS will eventually issue guidance. The firms that will look best when that guidance drops are the firms that already built a reasonable, documented protocol before they were required to.

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Part 3: The Three-Document Protocol That Protects Your Firm Now

None of this requires waiting for the IRS. The following three documents can be drafted in an afternoon, don't require legal counsel to produce a first version, and build your evidentiary position before guidance drops.

Document 1: Updated Engagement Letter Language

Add an AI disclosure clause to your standard engagement letter. The language should state that your firm uses AI-assisted preparation tools in its workflow, and that all returns are reviewed and signed by a licensed CPA who retains full professional responsibility for the work product.

The parallel framework already exists in legal ethics. ABA Formal Opinion 512 established that lawyers using AI must disclose that fact to clients when it materially affects their representation. Tax practice isn't bound by the ABA, but the underlying logic applies equally: if the preparation method has changed materially, clients should know. Updating your engagement letter costs nothing and puts the disclosure on record.

Document 2: AI Review Sign-Off Protocol

Write a one-page internal checklist that defines what "human review" means at your firm when AI has assisted in preparation. Specifically: which elements a CPA must independently verify before signing any AI-assisted return.

For a 1065, that might include: confirming K-1 allocations against the partnership agreement, verifying that special allocation elections are correctly applied, spot-checking input data against source documents for two or three high-value line items, and confirming that the final return matches the client's prior-year structure where no changes have occurred.

The act of writing this checklist is not just compliance theater. It defines the standard your firm holds itself to — and it becomes your documentation of due diligence if the work is ever questioned. A CPA who can produce a written review protocol that was followed is in a fundamentally different position than one who cannot.

Document 3: Output Retention Policy

Retain the AI-generated draft alongside the final signed return. Keep both.

If a return is later disputed, the AI draft shows exactly what the system produced before human review — and the difference between that draft and the final signed return demonstrates what the CPA's review actually changed. That record shows the review was substantive, not ceremonial. Without it, there is no way to prove that the human sign-off added value.

This does not require a new software system. It requires a file structure decision: save the AI output as a dated draft version in your document management system, alongside the final. That's it.

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What to Do This Week

These three documents take an afternoon to draft and can be templated across your entire practice. You do not need IRS guidance to make them useful. They are useful precisely because that guidance doesn't exist yet — and when it does arrive, you will have a documented protocol that predates the requirement.

Start with the engagement letter. Pull up your current template. Add two sentences about AI-assisted preparation and the CPA's retained professional responsibility. Send it to your next engagement.

Then spend 45 minutes writing the review checklist for your most common return type. You almost certainly already know what you check — you just haven't written it down. Write it down.

The firms that look best in the AI era are not necessarily the ones using the most advanced tools. They are the ones who built reasonable protocols before anyone required them to.

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Related Reading:

• The AI That Files Partnership Returns — What Basis AI's $1.15B Valuation Means for Small Accounting Firms
• The Startup That Wants to Automate Your Tax Prep — What Accrual's $75M Launch Means for Small CPA Firms
• AI Disclosure in Engagement Letters — What Every Professional Services Firm Needs to Update Now
• The AI Governance Gap in Professional Services Firms
• Colorado AI Act: What the Small Business Exemption Means for Your Firm

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