Under the SEBI (Substantial Acquisition of Shares and Takeovers) Regulations, 2011, an acquirer crossing which threshold of voting rights in a listed company is mandated to make an OPEN OFFER to acquire further shares?

Regulation 3 of the SEBI (SAST) Regulations, 2011 triggers the mandatory open offer when an acquirer acquires shares taking his aggregate shareholding/ voting rights to 25% (or more) of the target company. On such acquisition, he must make a public announcement of an open offer for a minimum of 26% of the shares. (Disclosure obligations, distinct from the open offer, arise at the 5% and 10% levels under the regulations.) 'Control' acquisition also triggers the offer. The 25% trigger and the 26% offer size are the numeric heart of the Takeover Code.