With only six days to go before postal votes drop through the letter boxes, the Scottish electorate should expect to know what currency they would use in the event of Scotland voting for independence.

Earlier this week, Crawford Beveridge, chairman of First Minister's Fiscal Commission Working Group, crossed the Atlantic supposedly to shed light on the matter. Apart from admitting it was entirely possible a currency union would not be agreed after independence, Mr Beveridge left us none the wiser.

The currency debate leaves little room for romance and does little to tug at the heart strings, but since few of us can live on love alone we need to know our money will be there when we need it and what it will be worth.

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The status of the Scottish currency is not an academic question, and will affect most aspects of Scottish life, whether paying household bills and pensions or paying for schools and hospitals.

Supporters of Scottish independence say the pound belongs to Scotland as much as the rest of the UK, and at the moment since Scotland is part of the UK they are right. The Bank of England guarantees the pound throughout the UK. If Scotland goes it alone, without a currency union, the Bank of England, supported by UK taxpayers, would no longer be able to guarantee Scotland's financial system.

The Bank of England would not be the lender of last resort in Scotland. Alex Salmond's Plan B may be to use the pound informally without a guarantee, known in economic circles as "sterlingisation". Since the financial institutions in Scotland would have no support, it is a high-risk strategy. A good analogy is driving a car without insurance.

Threatening to walk away from Scotland's responsibilities to pay a share of the UK's debts if there is no currency union hardly helps. Not only would the credit agencies take a pretty dim view, and make it harder for Scotland to borrow, the rest of the world might conclude Scotland would not be an honourable business partner.

Mr Beveridge warned sterlingisation could only be a stop-gap, so a long-term replacement would have to be found in Scotland. Unless there is an alternative of which no living economist has had sight, there are only two options: joining the euro or setting up a Bank of Scotland as the lender of last resort. Neither option is particularly palatable.

To set up a Bank of Scotland to behave as the Bank of England does now in the UK, the Scottish Government would have to build up enormous reserves, able to support any financial institutions in Scotland. Since these reserves would come from the public purse, every penny diverted to reserves would be a penny less to spend on childcare, pensions, and every other public service paid by the taxpayer.

Mr Salmond says he no longer wants to join the euro, but he might be left with little alternative if the draconian cuts needed to build up reserves proved unacceptable. Then he would have to dance to the euro tune. Firstly, there would be lengthy negotiations. The very notion of them being concluded in 18 months is a fantasy.

Secondly, the euro managers would be in charge. As countries throughout Europe struggle in the wake of the global financial crisis, Scotland would be expecting exceptional and unrealistic largesse to get a free pass to the euro.

Economists often leave those of us who are not au fait with high finance struggling to make sense of their jargon. The currency debate is of a different order. We need to know Mr Salmond's plans for currency, whether it's Plan B, C or D.

Love or hate them, sound financial institutions matter. Our economy depends on them. And if there is any residual doubt about the fragility of our economy, Sir Ian Wood, former chairman of the Wood group and an authority on the oil and gas industry, has made a dramatic intervention into the economic debate.

Scotland cannot bet the farm on the offshore oil and gas industry in Scotland's economic calculations, according to Sir Ian.

If ever we needed certainty it is now. Nothing can be more uncertain than not knowing the strength of currency.