Deal mechanics · Competition law
Antitrust Due Diligence
Antitrust diligence is not a footnote on regulatory — it is the workstream that decides whether the deal can close on your timeline, at your structure, or at all. This guide is for PE, corp dev, and advisors mapping competitive overlaps, HSR/merger control filings, gun-jumping risk, and remedy readiness before signing.
What antitrust diligence actually covers
Competition-law review of a transaction spans six pillars:
- Overlap map — products, customers, geographies, and pipeline vs buyer portfolio.
- Market structure — concentration, barriers, switching costs, and customer alternatives.
- Filing map — HSR and multi-jurisdiction merger control thresholds and timelines.
- Conduct risk — gun-jumping, information exchange, and exclusivity-period protocols.
- Agency history — prior investigations, consent decrees, and sector enforcement trends.
- Remedies & path to clear — divestitures, behavioral commitments, and walk-away economics.
Six pillars of antitrust due diligence
1. Competitive overlaps
Map horizontal products and services where buyer and target compete today. Include pipeline launches, adjacent SKUs, and portfolio company overlaps that counsel will treat as one economic group.
2. Market definition signals
Customer substitution evidence, pricing bands, geographic reach, and channel structure. You do not need a final SSNIP model in screening — you need honest ranges that survive first agency questions.
3. Filing & thresholds
Estimate HSR reportability and other mandatory regimes (EU, UK, Brazil, China, and national systems). Track size-of-transaction tests, control tests, and sector-specific screens that change deal calendar.
4. Gun-jumping controls
Clean teams, outside counsel walls, and no premature operational control. Integration planning is allowed; joint go-to-market and pricing coordination before close is not.
5. Agency & history
Prior second requests, abandoned deals, ongoing probes, and industry consent decrees. A clean target with a serial-investigated buyer still inherits timeline risk.
6. Remedies readiness
If shares are high, model what you would divest, who buys it, and how long ring-fence takes. Behavioral remedies are harder in horizontal cases; timeline buffers must be real in the SPA.
Antitrust diligence vs regulatory vs legal DD
| Workstream | Core question | Primary risk if weak |
|---|---|---|
| Legal DD | What contracts, claims, and corporate facts exist? | Missed liabilities |
| Regulatory DD | Is the target licensed and compliant to operate? | License or enforcement drag |
| Antitrust diligence | Can this combination clear agencies on time? | Delay, remedies, or blocked close |
| Commercial DD | Is the market attractive and winnable? | Wrong thesis; also feeds overlap analysis |
Antitrust diligence sits on top of commercial and legal facts: market attractiveness can become a clearance problem when the buyer already owns a large share of the same demand pool.
Red flags (deal-killer / high / watch)
| Severity | Signal | Why it matters |
|---|---|---|
| Deal-killer | High horizontal overlap in a 2–4 player market | Second request / challenge likely; remedies may gut thesis |
| Deal-killer | Ongoing agency investigation of either party in the same market | Clearance path uncertain; SPA risk allocation fights |
| High | No filing map for multi-jurisdiction close | Surprise waiting periods after exclusivity burns |
| High | Integration teams exchanging pricing or customer lists without clean team | Gun-jumping exposure and agency distrust |
| High | Customer complaints or RFPs citing reduced competition | Agency customer outreach will surface them |
| Watch | Vertical foreclosure theories (inputs + downstream) | Longer review even without horizontal share spikes |
| Watch | Killer-acquisition narrative (nascent rival) | Small revenue can still draw scrutiny in tech/life sciences |
| Watch | SPA long-stop with no antitrust effort standard | Walk rights and reverse break fees misaligned to risk |
Full antitrust counsel packages often run $50K–$500K+
Before you fund multi-jurisdiction merger control, screen the target publicly: market position, competitive set, prior agency signals, and portfolio overlap hints. A $49 first-pass diligence PDF helps IC decide whether the combination even deserves the specialist budget.
Sequencing: when to diligence competition risk
| Stage | Antitrust focus | Output |
|---|---|---|
| Screening / IOI | Obvious horizontal overlaps vs portfolio | Kill or continue with counsel budget |
| Pre-LOI | Filing likelihood, high-level share ranges | LOI conditions and long-stop realism |
| Confirmatory | Market facts, customers, documents for filing | HSR/Form CO readiness; clean-team rules |
| Signing → close | Filing submission, waiting periods, remedies | Clearance path; interim conduct compliance |
| Post-close | Remedy implementation if any; hold-separate | Agency commitments met |
Cost and timeline (indicative)
| Approach | Typical cost | Typical time | Best for |
|---|---|---|---|
| Public first-pass screen | $49–$200 | Hours–days | IC triage, multi-name shortlists |
| Outside counsel overlap memo | $15K–$75K | 1–3 weeks | Mid-market LOI readiness |
| Full multi-jurisdiction package | $50K–$500K+ | Weeks–months | Reportable deals with real overlap |
| Second request / Phase II defense | $1M+ common | Months | High-share horizontal combinations |
Use the cheap screen to avoid paying Phase II money on a thesis that should have died at IOI.
50-point antitrust diligence checklist
Overlap & markets (1–10)
- Product/service overlap list vs buyer and portfolio companies
- Geographic markets where both sell today
- Pipeline products that will compete within 24 months
- Customer overlap (top accounts shared)
- Supplier overlap and dual-source risk
- Share ranges (public + management) by candidate market
- Number of credible competitors remaining post-deal
- Switching costs and multi-homing patterns
- Price levels and recent competitive RFPs
- Adjacent markets that agencies may expand into
Filings & jurisdictions (11–20)
- HSR size-of-transaction estimate (confirm current thresholds)
- Other mandatory filings (EU, UK, and national)
- Voluntary or call-in risk jurisdictions
- Foreign investment / CFIUS-style screens if any
- Sector regulators with concurrent review
- Filing fees and preparation lead time
- Waiting period calendar vs SPA long-stop
- Who files (buyer vs joint) and document custodians
- Translation and local counsel needs
- Prior filings on similar deals by either party
Agency history & documents (21–30)
- Prior investigations or consent decrees
- Abandoned deals and stated reasons
- Internal ordinary-course docs on competition (4(c)/4(d)-style)
- Board decks discussing market power or pricing power
- Customer complaint files
- Trade association memberships and information exchanges
- Non-competes and market allocation history (red flag if any)
- Past agency interviews or second requests
- Industry enforcement priorities this year
- Press or legislative focus on the sector
Conduct & interim period (31–40)
- Clean-team protocol drafted and trained
- Outside counsel walls for sensitive data
- No joint customer pricing or bidding before close
- No operational control of target pre-close
- Integration planning scope limited to permitted planning
- Employee non-solicit / non-hire rules observed
- Public communications reviewed for competitive claims
- Document hold for potential second request
- Q&A log that does not create bad ordinary-course paper
- SPA effort standard and reverse break fee sized to risk
Remedies & close path (41–50)
- Divestiture candidate assets identified (if high share)
- Likely buyers for divestiture packages
- Behavioral remedy feasibility (usually limited horizontally)
- Hold-separate / ring-fence operating model
- Cost of remedy vs deal NPV
- Walk-away rights if clearance fails
- Extension mechanics for long-stop
- Financing conditions interaction with delayed close
- Employee and customer communication plan on delay
- Post-close compliance owner for any commitments
Worked diligence questions (IC-ready)
- Where do we compete with the target today, and which portfolio companies count in the same economic group?
- What is our honest share range in each candidate market, and what do customers say about alternatives?
- Which filings are mandatory, and does the SPA long-stop survive a second request?
- What ordinary-course documents would embarrass us if an agency read them on day one?
- If agencies demand a remedy, what do we sell, and does the thesis still work?
- Are exclusivity-period teams following clean-team rules, or are we already gun-jumping?
- Has either party been investigated or forced to abandon a similar deal in the last five years?
- What is the reverse break fee and effort standard if clearance fails or is conditioned?
How dodilligence fits
dodilligence delivers institutional-style diligence PDFs from public and structured sources: business model, competitive position, risk register, and IC workplan. Use it to triage whether a target’s market position and competitive set make antitrust a first-order IC issue before you open a multi-jurisdiction counsel workstream. It is not legal advice, not a merger filing, and not an agency clearance opinion.
Screen the target before you underwrite clearance risk
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Name a company. Get a diligence PDF with competitive context, risk flags, and IC questions — including whether competition-law risk belongs on the first page of the IC memo.