The price of Royal Mail shares being sold off by the Government will be announced after the close of stock market trading today.
Business Secretary Vince Cable has approved the price and details of how the stock will be allocated between institutional and retail investors - which is also due to be made public.
More than 700,000 applications to buy shares had been made by the time of Tuesday night's deadline and the shares are widely expected to be priced at the top of its 300p to 330p price range, valuing the business at up to £3.3 billion.
Conditional trading on the stock exchange begins tomorrow amid expectations that the share price could rise dramatically to around 400p.
On offer are shares representing up to 52.2% of the value of the company. A 10% stake is being allocated free to 150,000 employees.
Members of the public - or retail investors - are expected to be allocated around 30% of the shares and the more than 700,000 applications received so far means this chunk is up to seven times oversubscribed.
Ministers were reported to be holding emergency meetings about the final allocation today. Business Minister Michael Fallon said he was "committed to making sure small investors get their fair share".
Mr Cable has been forced to defend the privatisation against claims that it has undervalued the public assets being sold, including large sites in London where property prices have been rising rapidly.
MPs have voiced concern that the sell-off will be highly lucrative for speculators, hedge funds and investment banks rather than the public.
Next week, results of a ballot of Communication Workers Union members are expected to back industrial action over issues linked to privatisation.
Demonstrators dressed as robbers will protest over the share sale outside the Stock Exchange tomorrow.
Royal Mail says the flotation will give it flexible access to private capital, which will be a "positive step" for the universal postal service.