Potential Scottish taxpayers will be contacted in the coming weeks as part of preparations for the introduction of the Scottish rate of income tax.
The letters are intended to confirm the accuracy of HMRC's records of taxpayers who live in Scotland and will pay the new rate in the 2016-17 tax year.
They will be sent to around 2.6 million people.
The Scottish rate of income tax, which will be announced by the Scottish Government on December 16 in its Budget, comes into effect on April 6 and will be paid by UK taxpayers who live in Scotland, regardless of where they work.
Income tax will be reduced by 10p in the pound for Scottish taxpayers, but they will then have to pay a new Scottish rate which could be 10p, or more or less than 10p.
Those paying the new rate will see their tax code prefixed by an "S" and their income tax will continue to be collected from pay and pensions in the same way as it is now.
Edward Troup, tax assurance commissioner and second permanent secretary at HMRC, said: "HMRC is taking the next step towards implementing devolution of tax powers to the Scottish Government.
"The new tax rate will apply to everyone who lives in Scotland. If we've got your address right, there's no need to do anything - the small number who need to change their address details can do so quickly and easily online at www.gov.uk/tell-hmrc-change-of-details."
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