HMRC announced last year that it intended to closely examine the rental incomes of buy-to-let landlords. According to Nationwide, some 500 letters have so far been sent to property owners, seeking clarification of any rental incomes.

Andy McQueen, managing director of The Mortgage Works and UCB Home Loans, said landlords who are new to the buy-to-let market may be unaware that they have to declare details of rental income, even if the revenue is not taxable.

He said: “HMRC can use stealth tactics to find information on landlords who may not have declared rental incomes, including targeting lettings agents and reviewing Stamp Duty records. Buy-to-let investors could find there are serious ramifications to not declaring rental incomes if they are hit with a backdated tax bill.”