Vodafone is on the verge of selling its stake in America's biggest mobile phone company in a 130 billion US dollar (£84 billion) deal that is so big it is expected to provide a significant lift to the UK economy.
The company has confirmed it is in "advanced discussions" to dispose of its 45% interest in Verizon Wireless in what would be one of the biggest transactions in corporate history.
Cash from the deal returned to UK shareholders is expected to provide what is effectively a fresh dose of quantitative easing to stimulate the economy - to add to the Bank of England's £375 billion programme of asset purchases.
Pension funds with investments in the widely-held stock also stand to benefit.
However there is likely to be controversy over the way the deal is arranged amid reports that Vodafone's tax liabilities will be minimised by completing the transaction through its Luxembourg subsidiaries and other offshore companies.
The UK firm's board was said to have met yesterday to approve the deal to sell its stake to its US partner Verizon.
In a statement, it said: "Vodafone confirms that it is in advanced discussions with Verizon Communications Inc regarding the disposal of Vodafone's US group whose principal asset is its 45% interest in Verizon Wireless for 130 billion US dollars."
It said the deal would comprise a mixture of Verizon shares and cash.
Shareholders in FTSE 100-listed Vodafone are predicted to receive a special dividend of up to £40 billion.
According to financial services group Hargreaves Lansdown, an investor holding £5,000 of Vodafone shares might receive £2,000, with no further tax to pay as long as it is held in a pension fund or individual savings account (ISA).
Investors without direct shareholdings are likely to benefit through their pensions, with many funds holding up to 10% in Vodafone stock.
Shares in the mobile phone giant have leapt more than 8% over the past week in anticipation of the deal.
Asked whether David Cameron was concerned about the possibility of Vodafone taking steps to minimise UK tax liabilities on the deal, the Prime Minister's official spokesman said: "I wouldn't comment on the tax affairs of individual companies."
Margaret Hodge, chairwoman of the Commons Public Accounts Committee which has investigated corporate tax-dodging, said she wanted the deal to be examined in detail.
The Labour MP said: "Clearly there are concerns on this deal. I just want some assurance that HM Revenue and Customs (HMRC) will be going through this deal with a tooth comb to ensure that the taxpayer gets the proper benefit under the law of the tax that Vodafone should pay on this massive windfall profit that they are making."
Mrs Hodge urged HMRC to ensure there was no "aggressive tax avoidance" in the way the deal was done.
Senior HM Revenue and Customs official Ruth Owen told the committee: "I can't comment on this particular taxpayer's tax affairs, but I would assure the committee HMRC plays its full role keeping very close to every large business to make sure they are paying the tax that is legally due."