The most likely overall outcome for taxation is that rUK would treat Scottish individuals and companies in the same way as it treats any other country's individuals and companies (and vice versa). Scotland will need to establish its own financial regulator and resolution authority and make arrangements for continuing the licences and supervision of Scottish firms. Arrangements for pension investments and payments will be required.
The practical issues that arise on separating Scotland from rUK cannot be underestimated, despite the existence of a Scottish Government since devolution in 1999. Everything run on a UK-wide basis must be split.
Laws that are in force in Scotland and in rUK on independence day will continue in force, but both countries need to look at their statute books in order to ensure that they meet the requirements of each country's new or revised form. For example, the Scottish judges sitting in the (rUK) Supreme Court will, presumably, be removed; the almost innumerable UK statutory references to Scotland may need removal or amendment; and the Royal Charter establishing the BBC provides for there to be a trust member for Scotland, who will, presumably, lose his post on independence day. The list is endless.
The practical issues go beyond the two Governments. Anyone with operations in, or dealings with, Scotland needs to consider how the changes required for, or wrought by, independence affect their position. Much of the work to achieve separation will require negotiation between Scotland and rUK, which will be difficult, quite possibly fractious, given the divergence of interests between the two. Extensive quantities of black coffee may be needed to see people through late nights of negotiation, but, if anything is to be achieved, any stimulant must be supplemented by a huge amount of goodwill on all sides.