The HM Revenue & Customs has been accused of "bully boy tactics" for sending high earners letters asking why they are not paying more tax.
Around 1,000 letters have been issued to people who have an income of more than £150,000 but are paying less than 22% in tax.
The letters state: "We can see from your Self Assessment tax return... that your effective rate of tax is lower than the average for people in your income bracket.
"There may be reasons why your effective rate of tax is correct. But it could mean that there is something wrong with your self assessment."
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