Konstantin i Elena will offer for sale 877,235 rights to which no shares have been subscribed, BSE said in a notice.
Orders can be placed between 1315 and 1345 local time on April 10.
Last month, Konstantin i Elena Holding kicked off its capital increase, in which it is offering 1 million new voting shares at 22 levs ($12.17/11.25 euro) apiece. Each right held corresponds to some 0.433 new shares in the company.
Shares in Konstantin i Elena last traded on April 4 when they closed at 22.00 levs on the Bulgarian Stock Exchange, bourse data show.
(1 euro = 1.95583 levs)