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The 'SCOXX' index? How the vote has hit shares

A hypothetical Scottish share index, made up of companies based in Scotland that are currently listed in the U.K., has been left relatively untouched by the looming referendum, performing in line with the broader U.K. index.

The index -- formulated by data-provider Markit and formed of 12 companies headquartered in Scotland and listed on the FTSE 350 -- has returned 15.3 percent since the start of 2013 compared to the wider index's 17 percent.

Read MoreUK opposes Scottish exit amid bank run fears

Hundreds of Yes supporters gather in George Square to show their support for the independence referendum
Jeff J Mitchell I Getty Images

While the returns are fairly in line with the broader index of U.K. stocks, the Scottish index has proved more volatile Markit, which compiled the index, said.

Financial companies including Aberdeen Asset Management, insurer Standard Life and Royal Bank of Scotland (RBS) dominate the index, making up 40 percent of its weight.

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But both RBS and Lloyds have already announced plan to re-domicile to England in the event of a yes vote.

Debt rating woes

As well as the hypothetical stock index, Scotland has also been given a potential sovereign risk rating in the lower BBB region, one notch above junk, by country risk rating group IHS.

Clear policy uncertainties for Scotland would be detrimental to its sovereign rating if it votes for independence, IHS said, leading to a lower rating in the BBB region.

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Scotland would face slightly higher borrowing costs than the UK's AA rating and these higher borrowing costs would likely "cascade down to Scottish domiciled banks, corporates and individuals," IHS director of sovereign risk analysis, Jan Randolph, said.

"Scotland has a somewhat 'out-sized' financial sector that is presumed to generate a modest services' surplus that would likely disappear after independence given the uncertainties or absence of a central bank support," he said.

"There is already clear evidence that a number of Scottish financial institutions would move at least their headquarters south of the border in the event of a vote for independence," he added.

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