Retail and institutional investors will be allowed to buy shares at the same time under new initial public offering rules that aim to make it easier for companies to sell shares simultaneously in the mainland and Hong Kong, the South China Morning Post reported. Under the old mainland system, the listing company would talk to potential institutional investors to gauge how much they could fetch for the stock, and then institutional investors would bid for the shares in a process known as "accumulative bidding" or book-building, enabling the firm to set a final price. Retail investors would then be allowed to buy shares at the same price. Simultaneous bidding by individual and institutional investors should cut two days off the mainland initial offering process, the newspaper reported. Small and medium-sized enterprises will be allowed to skip book-building entirely, trimming the process by four more days and saving the selling company money. The changes are timed with Industrial and Commercial Bank of China's initial public offering of up to US$21 billion in mainland and Hong Kong shares due as early as next month.