About 400,000 Vodafone shareholders, who originally invested in the public flotation of Eircom 15 years ago, will avoid a tax bill when they share a windfall of at least €27.5m.

The Revenue Commissioners have confirmed that those original investors will not get a bill for the Capital Gains Tax when Vodafone's US business is sold off as proposed next month.

The reason is that small investors are still operating at a loss on their Eircom investment, a portion of which eventually became Vodafone stock through a sell-off of the company.

A briefing document published by the Revenue Commissioners outlines the implications of Vodafone deciding to sell its 45% stake in the US business Verizon Wireless to Verizon Communications.

Almost 400,000 Irish investors who directly hold shares in Vodafone will have received correspondence outlining its "return to value strategy". Vodafone is set to distribute almost €62 billion back to its shareholders in a mixture of cash and Verizon shares.

Taking the value of December 6 as a guide, shareholders would be entitled to €0.89 in Verizon shares and €0.36 in cash for each Vodafone share.

Having analysed the figures, which they say are provisional, the Revenue Commissioners said there would be no chargeable gain - and therefore no Capital Gains tax payable by those former Eircom shareholders who take the windfall as capital.

Vodafone expects to announce the exact number of Verizon shares that investors will be entitled to on February 19 and the cash amount they will get on February 21.