A senior UK Government official will appear today before MSPs investigating new devolved powers for tax and borrowing.
Edward Troup, the second permanent secretary at HM Revenue and Customs, has responsibility for the Scottish rate of income tax which is due to come into effect in two years.
He is expected to face questions on the costs and operation of the tax, as well as the IT systems.
Holyrood’s Finance Committee is looking at the transfer of power under the Scotland Act 2012.
The new tax rate means the UK Treasury will deduct 10p from standard and upper rates of income tax in Scotland and give MSPs the power to decide how to raise cash.
The power is expected to come into force in April 2016, just before the next Holyrood election.
The Scottish Government hopes to have achieved full statehood by March 2016, giving MSPs full control of tax powers.