5 Best AI Tools for Contract Due Diligence in 2026

When lawyers perform supply-chain review, due diligence in an M&A deal, or any other transaction, the goal is to understand contracts. That means knowing what clients are signing, what commitments and benefits they’re taking on, and what could go wrong once the deal closes.

Reliance on AI has become standard in the contract analysis phase because it eliminates manual work. AI helps identify potential risks and improves the speed of contract analysis across hundreds of documents when time is tight. 

Some tools are built as full-diligence platforms within a virtual data room (VDR). Others, like Spellbook, fold diligence tasks into Microsoft Word, where it supports multi-document reviews, benchmarking, and redlining without pushing information into a separate system. Though Spellbook is not a standalone “diligence platform,” lawyers use it for the same core legal work that determines diligence quality and speed.

Key Takeaways

• AI is now a standard part of contract due diligence because it reduces human error, cuts manual review time, and ensures consistent results across large batches of agreements.
• Different tools solve various parts of the due diligence workflow. Some operate inside a virtual data room and contract lifecycle management (CLM) systems, while others support diligence directly in Word at the clause level.
• Spellbook is the best fit for teams that start diligence in Microsoft Word and want AI to assist with review, redlining, precedent checks, and benchmarking without moving documents to another platform.

The Best AI Tools for Contract Due Diligence in 2026

Not all AI tools that touch contracts are built to support the same deal efforts. If your team is comparing options or building a diligence stack for 2026, here are five AI tools leading the market in contract due diligence today.

1. Kira (Litera)

Kira is one of the most mature AI tools built for M&A contract review. It is trusted for bulk work because it extracts key information from large sets of contracts with high accuracy. Kira is best suited for large firms with recurring enterprise M&A work that need consistency and repeatability across many deals. 

2. Imprima AI Due Diligence

Because Imprima combines AI with a VDR, reviewers do not need to export documents into a separate review tool. Its AI layer can detect hidden clauses and conditions in contracts and surface them within the same cloud workspace documents. It is built for deal teams that operate fully in the cloud, where the same platform hosts, sorts, and reviews files. Imprima is a strong fit for sell-side processes and high-volume reviews where keeping all activity inside a VDR is the priority.

3. Luminance Diligence

Luminance is an AI review system built for high-volume contract sets. It presents findings through dashboards and visual heatmaps, enabling teams to see patterns and outliers without opening every file. It is widely used in cross-border or multi-language reviews where volume makes manual work unrealistic. Its strength is triage at scale. It provides insights into contract clauses across a corpus and lets reviewers drill down only where needed.

4. SpotDraft AI

SpotDraft is a contract lifecycle management (CLM) platform with an AI layer for due diligence-style review. Because it sits inside a CLM workflow system, it is often chosen by teams that want routing, approvals, and audit trails alongside contract analysis. Its AI engine can evaluate contract terms and flag language for inclusion in routing rules or playbooks. SpotDraft makes most sense when diligence is one step inside a broader contracting process, not a stand-alone M&A event.

If you’re exploring CLM-centered review paths, see how law-firm contract automation software is being adopted across transactional teams.

5. Harvey AI

Harvey is a broad AI co-pilot for legal teams, not a product built only for M&A or contract diligence. It can efficiently summarize lengthy contracts, run Q&A across large document sets, draft memos, and support research. It shows promise for transactional teams because it extracts essential data from contracts and can be pointed at deal folders to answer structured questions. But its scope is intentionally wide: litigation, regulatory, corporate, and internal policy use cases all live in one system.

Recommended Reading: Best AI Contract Redlining Tools

Word-Based Due Diligence vs. Platform-Based AI Tools

The tools above are built for different stages of diligence. The key difference is not capability, but where and how lawyers work. The comparison below shows how each approach differs from Spellbook’s Word-native model.

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What to Look for in an AI Tool for Contract Due Diligence

Speed alone is not the whole test. The rise of AI in due diligence makes it even more important to distinguish diligence-grade tools from generic AI that only “reads” the document.

Clause & Risk Detection

Proper AI tools spot non-standard or potentially risky clauses and flag when a required term is absent, watered down, or drafted in a way that shifts liability. The value is not just speed. It’s also confidence that nothing material slipped through because it looked “close enough” on first read.

Handling Multiple Documents at Scale

Due diligence is rarely a one-document exercise. The ideal AI tool must perform well with hundreds of agreements and still scan documents quickly without breaking structure or losing context across versions. It supports multi-document work in Word, enabling teams to triage, compare, and annotate at volume without moving files into a separate interface. That makes it practical for associate-level review and repeatable diligence work.

Recommended Reading: Best AI Legal Document Comparison Software

Legal Domain Knowledge

Generic AI can read text, but that is not enough for diligence. The best system must be legally trained on real contracts and fine-tuned to understand how risk actually manifests in deals. Jurisdiction matters, too. The proper AI tool analyzes regulatory compliance and adapts to local standards, avoiding false alarms on clauses that are standard in one region but risky in another.

Integration With Existing Workflows

A tool that lives outside counsel’s daily workspace adds friction. Must they leave Word to review and analyze contracts, or can they stay where contract drafting currently happens? 

An ideal AI tool runs in Microsoft Word, enabling lawyers to review and edit in the same place they negotiate without shuttling files between systems. That reduces toggling and improves contract consistency as changes are made line by line.

Suggestive Edits, Not Autopilot Changes

The proper AI tool proposes options and highlights contentious points, but leaves judgment and drafting to humans. The ideal AI tool suggests edits and revisions without silently rewriting text or pushing changes live. It keeps lawyers in control of the language while reducing the mechanical work of review, redlining, and responding to flagged issues.

Benchmarking and Clause Comparison

The best AI tool compares clauses against established standards or public precedent and helps compare contract versions to identify where language has been tightened or softened across drafts. This gives teams a grounded baseline for negotiation, rather than treating each clause as a new question.

How Spellbook Supports Your Contract Due Diligence Tasks

Most due diligence contract work does not happen in a data room or CLM dashboard. It occurs in Word, line by line, before any contract is escalated, priced, or signed. Instead of pulling contracts into a separate AI interface, Spellbook brings AI into the document. Review and redlining happen where lawyers make decisions. This keeps the work defensible, contained, and auditable, without adding another system to the stack. In practice, that looks like:

• Inline automated review, redlines, and clause guidance
  Diligence decisions are made at the clause level, not in a dashboard. Spellbook works in Word, surfacing potential risks, obligations, and pressure points as you read and draft instead of forcing a jump to a separate system.
• Volume without leaving Word
  Early diligence often starts with a stack of agreements. Spellbook lets lawyers triage, annotate, and prepare multiple contracts in a single Word session, ensuring nothing is lost during hand-offs.
• Benchmarking against precedent
  Spellbook compares language to prior deals and patterns, as well as to industry standards. Reviewers see not only “what changed” but also whether the current version sits above or below an acceptable baseline.
• Native to the drafting environment
  Because Spellbook lives in Word, where lawyers already negotiate, the review and the fix happen in one place. No upload cycles, no context switching, no fragmentation of the record.

Spellbook is the best fit for teams that begin diligence in Word and want AI to automate tedious manual work while maintaining control of legal judgment. Try Spellbook on a contract and see the difference inside Word in minutes.

Frequently Asked Questions

How Does AI Improve Accuracy and Efficiency in Due Diligence?

AI accelerates due diligence reviews by handling mechanical reading and contract grouping, ensuring consistent results across reviewers. It reduces miss-risk by flagging deviations and missing terms that a first pass might overlook. In Spellbook, benchmarking and clause detection raise accuracy by comparing language to known precedent directly in Word, so fixes happen at the point of review.

Can AI Identify Compliance Issues in Contracts During Due Diligence?

Yes. AI can surface language that appears non-compliant or incomplete, e.g., flagging the absence of a General Data Protection Regulation (GDPR) clause or a weak anti-bribery warranty. Spellbook can highlight those gaps in Word, but it does not independently determine compliance. It directs counsel to what must be reviewed.

Do AI Contract Tools Store Sensitive Client Data?

Policies vary. Some AI vendors retain and reuse uploaded contracts, while others do not. Always review the privacy and retention policy before using any AI tool.

Spellbook is compliant with GDPR, the Personal Information Protection and Electronic Documents Act (PIPEDA), and the California Consumer Privacy Act (CCPA), and does not keep contract data after the active session. It processes documents for review but does not train on client materials.