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Comparison

Mandatory vs voluntary bid

A voluntary bid is launched at the bidder's election. A mandatory bid is required by law once the bidder crosses a control threshold (non-US regimes).

Attribute Voluntary bid Mandatory bid
Trigger Bidder elects to launch Required by law once acquirer crosses control threshold (typically 30%)
Where common All jurisdictions including US EU, UK, Hong Kong, Australia, most Commonwealth — not US
Price floor Set by bidder; subject to Williams Act / fairness rules Highest price paid by acquirer in defined lookback (typically 6–12 months)
Coverage Can be partial or full (depending on jurisdiction) Almost always for 100% of remaining shares
Conditional Yes — minimum tender, financing, regulatory conditions standard Limited — most jurisdictions restrict conditionality on mandatory offers
Protective effect on minorities Less — minorities can be left as permanent minorities Strong — every minority gets the chance to exit at the highest price
Strategic use Standard structure for friendly and hostile takeovers in US Imposed by regulation rather than chosen; common path for stake increases above 30%

When the comparison matters

The mandatory bid rule is one of the most consequential structural differences between the U.S. tender-offer regime and most non-U.S. takeover regimes. A 30% accumulation in the U.S. triggers Schedule 13D disclosure and Williams Act tender-offer rules; the same accumulation in the U.K., E.U., Hong Kong, or Australia triggers a mandatory bid for 100% of remaining shares at the highest recent price.

Why the U.S. doesn’t have one

The Williams Act focuses on disclosure rather than mandating equal exit — the federal regime trusts state corporate law and fiduciary-duty doctrine to protect minorities post-acquisition. State fair-price provisions and §203 partially fill the gap, but the structural protection is materially weaker than EU-style mandatory bids.

Practical posture for cross-border buyers

A would-be acquirer planning a 30%+ stake in a non-U.S. target needs to model the mandatory-bid trigger upfront — crossing the threshold without intent to bid for 100% is rarely viable.

Guides

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