An anti-trust filing is the mandatory pre-merger notification to competition authorities when a transaction exceeds statutory size thresholds, pausing close until waiting periods expire or clearance is granted.

How it works

In the U.S., parties file under Hart-Scott-Rodino when deal and buyer size tests are met (thresholds adjust annually). Buyers pay a filing fee; both sides supply ownership and revenue data. Initial waiting period is often 30 days—longer if regulators issue a second request for deep review. EU, UK, and other jurisdictions run parallel regimes for global strategics.

Most venture-backed exits fall below HSR thresholds, but larger strategic sales and PE roll-ups cross them routinely. Purchase agreements allocate risk via termination fees and outside dates if anti-trust clearance fails.

Why it matters

• Founders: LOI timelines should include regulatory buffer; employee announcements wait until clearance risk is understood.
• Investors: Competitive overlap between buyer and target increases second-request probability.
• Buyers: Remedies may require divestitures—renegotiating price if scope shrinks.

Common mistake

Announcing a done deal to employees before filing clearance. Regulators or leaking customers can complicate a sensitive review.

Related ideas

HSR waiting period, merger control, acquisition timelines, and add-on acquisition roll-ups.