Scottish Widows will appear in the Supreme Court on 16 May over a tax refund dispute with HMRC.
The provider is appealing an earlier decision given in favour of HMRC.
A Scottish Widows spokesperson said the provider overpaid tax in 2001 and is appealing for a refund.
Between 1999 and 2001, Scottish Widows was demutualised and its business bought by Lloyds TSB Group.
In 2000, Scottish Widows plc was formed by Lloyds to acquire the business of the Scottish Widows Fund and Life Assurance Society as it was then.
Scottish Widows plc then created a fund to maintain its long-term insurance business and, within it, a capital reserve account holding some shareholders' capital was established.
In 2001, Scottish Widows suffered trading losses and transferred money from the capital reserve account to cover those losses.
HMRC contested during a court of session (the Scottish equivalent of the court of appeal) on 16 June 2010 that this transferred money should be counted as a receipt rather than a loss for tax purposes.
The case will now be taken up in the Supreme Court. If the Supreme Court rules in favour of HMRC, the transfers will be seen as a £1bn receipt, but if Scottish Widows wins the case, it will be due a tax rebate on the money.
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