DEVOLUTION of more taxes to Scotland would require an extended timescale beyond 2016, introduce more complexity to the revenue system and could overstretch an already strained HM Revenue and Customs, tax experts have warned.

Asked by Tory backbencher Alok Sharma about how much confidence there was in avoiding a "total disaster in the tax system" should greater tax powers be devolved as a result of the Smith Commission, Chas Roy-Chowdury, head of taxation at the Association of Chartered Certified Accountants, said if more powers were devolved on top of those already planned for 2016, "then we need perhaps to think about extending that timeframe".

He told the Commons Treasury Committee: "There's nothing worse than having a dysfunctional tax system, the administration burden going up, knee-jerk reactions, introducing anti-avoidance measures. It needs to take the time it needs to take.

"Clearly, there's going to be greater devolution than was proposed for 2016, we need to look at extending that timetable to make sure we get it right."

A senior Coalition source has already pointed to any new tax powers, on top of the introduction of the new Scottish income tax rate planned for 2016, taking at least three years from the time of this year's referendum result.

Mr Roy-Chowdury explained the HMRC did not seem to think there was a huge problem in identifying who were Scottish taxpayers but suggested other problems could emerge.

"For example, lorry drivers going to and fro, people living in England but working in Scotland; there must be a lot of those...There could be a real mish-mash of different areas, which could cause problems."

Patrick Stevens, tax policy director at the Chartered Institute of Taxation, pointed out how, depending on how far more powers were devolved, it would lead to "far more self-assessment tax returns required from people who had a variety of different sorts of income."