Small shareholders in mobile operator MMO2 have until Wednesday afternoon to decide whether to sell their shares back to the company.
MMO2 plans to pay its first dividend later this year
Under the offer, MMO2 shareholders can sell their shares to the company for 5p more than the price quoted on the London Stock exchange.
But the offer is only for shareholders registered with the company.
More than a million people could take up the offer, designed to cut MMO2's share dividend payment costs.
MMO2 intends to pay a share dividend later this year.
The MMO2 offer in detail
Shareholders can choose to sell their shares to MMO2 for 5p above the price on the London Stock Exchange
MMO2 will not charge a dealing fee and stamp duty will not be due on the sale
Registered shareholders who do not turn down MMO2's offer will be presumed to have agreed to sell
MMO2 wants to buy back 300 million shares - if more shares are offered to it, then individuals with the fewest number of shares will be bought out first
People who hold MMO2 shares in nominee accounts will have to become a registered shareholder to be able to take up the offer
But MMO2 claims it has too many shareholders and the cost of paying a dividend would be prohibitive.
It was de-merged from BT in 2001, with all BT shareholders receiving shares in MMO2.
This meant MMO2 inherited more than a million small BT shareholders, with 63% of its shareholders owning just 3.5% of the company.
MMO2's offer has courted controversy on two fronts.
Firstly, MMO2 shareholders with their shares in a nominee account - an account held in the name of a stockbroker rather than an individual - were told they had to become a registered shareholder in order to take advantage of the offer.
The logic for the company was clear - MMO2 administers the payment of dividends to registered shareholders, while dividend payments to nominee accounts are administered by a stockbroker.
But the cost and time involved in becoming a registered shareholder is likely to have deterred many shareholders.
Secondly, registered shareholders who do not turn down MMO2's offer will be presumed to have agreed to sell. This has prompted some in the City to accuse the firm of "bouncing" small shareholders out of the door.
However, Hilary Cook, director of investment strategy at Barclays private clients, has said that MMO2's offer was "generous" and a "good deal" but choosing to sell up could mean missing out on future share price growth.
MMO2 is using the share offer as an opportunity to drop the MM from the company's name and it will in future be known as O2.
The latest time for receipt of forms is 5pm on Wednesday 9 March.