How do we make sure that we can collect tax and pay social security benefits?
What do we need to do to be able to collect taxes after independence?
Scotland already has a body called Revenue Scotland which has the basic tax details for everyone resident in Scotland. It only collects a small proportion of taxes at the moment but extending it to collect all taxes is primarily a matter of staffing and strengthening IT systems so is comparatively routine. What is a little more complicated is collecting business taxes as these are currently largely the responsibility of the UK (though businesses with premises in Scotland will be registered for non-domestic rates). Data on companies operating in Scotland would be transferred from the UK to Scotland during negotiations and any gaps would need to be worked on during transition.
And paying social security benefits?
It's much the same issue. Scotland has the skeleton of a social security system but during the transition it would need to build up its systems and have the UK's data and responsibilities transferred to it.
What about pensions?
This is often raised as a major issue for independence but the reasons for this are political rather than technical. The UK has a revenue system of pensions rather than a contributory one so we'll be paying the same pension to the same people in the same way as in the UK. There is nothing much to disentangle.
What about people who have paid towards the UK pension their whole life?
This is a hotly-contested grey area. The current rules say that anyone who has contributed enough in National Insurance Contributions that they are eligible for a full UK pension will be paid that pension irrespective of where they are located on retirement – the UK pays the pensions of people who have retired to other countries and there is no obvious exemption which means that they wouldn't pay Scottish citizen's pensions. However, in all likelihood this is a matter that would be resolved during transition negotiations and Scotland might negotiate to have UK liabilities offset against Scotland's debt share. Either way, Scotland would be able to pay pensions as the UK does now.
So tax and social security would be exactly the same after independence?
This is one of the areas which is tricky to deal with politically. The UK tax system is unsupportably complex and its social security system aggressive and unpleasant. Enshrining these for day one of independence is very hard to justify, but any changes (even just simplification or 'cleaning up') imply political decisions. A solution might be a cross-party summit after a vote for independence to negotiate an interim solution. After that tax and social security policy will be a matter for elected governments.