Definition
A partial tender offer is a tender offer for less than all of the target’s outstanding shares — for example, an offer for 51% of shares to acquire control without buying out minority holders.
Why it matters
Partial offers are sometimes used to gain control with less capital. They are subject to special pro-rata acceptance rules under Rule 14d-8: if more shares are tendered than the offer can buy, accepted shares must be allocated pro-rata among all tendering shareholders.
Risks
Partial offers are often viewed as coercive because remaining shareholders may end up holding minority stakes in a now-controlled company at uncertain future prices. Some U.S. states (and many non-U.S. jurisdictions) restrict or prohibit partial offers, requiring acquirers crossing certain thresholds to make an offer for 100% (a mandatory bid).
Distinction
A two-tier tender offer is a structured variant where the front-end is a partial cash offer at one price followed by a back-end merger at a (usually lower) price.