By Vishwadha Chander
(Reuters) - Siris Capital has submitted a non-binding proposal to buy British outsourcer Equiniti for 624.3 million pounds ($864.6 million) in cash, the U.S. equity firm said on Monday, confirming months of media speculation about a bid.
Equiniti, shares of which rose by as much a fifth, said it had received a "highly conditional non-binding proposal" from Siris earlier in the day.
The 170-pence-per-share bid is Siris' fifth approach to Equiniti, Sky News reported, adding its most recent attempt was in January. (https://bit.ly/32r5Xwx)
Equiniti, which works with more than two thirds of the companies listed on the FTSE 100 index, said its board would evaluate the offer and "strongly advised" its shareholders not to take action in the meantime.
Siris said further announcements will be made, but there is no certainty that a formal offer will be made. It has until May 17 to make a firm bid or walk away under the UK's takeover rules.
Equiniti's stock price has soared 19% since reports of takeover interest first emerged in early February. Shares were up another 16% at 158.8 pence by 0829 GMT.
Listed on the UK mid-cap index, the company holds 70 million shareholder records, sends 90 billion pounds in payments each year and looks after 1.1 million share plan investors, according to its website.
In January, Equiniti said it was in discussions to divest a key part of its financial services.
($1 = 0.7221 pounds)
(Reporting by Vishwadha Chander and Aniruddha Ghosh in Bengaluru; Editing by Rashmi Aich, Kirsten Donovan)