The Barnett Formula determines what share of UK government spending goes to Scotland, Wales and Northern Ireland.
Named after the former Chief Secretary to the Treasury, Lord Barnett, the formula has been in use in Scotland and Northern Ireland since 1979, and in Wales since 1980.
It has resulted in higher spending per capita in the devolved nations than in England.
A House of Lords Select Committee recently published a report recommending that the formula no longer be used. Lord Barnett was among those who gave evidence to the committee and called for the formula to be scrapped or redesigned.