In 2019, HMRC found 11,129 landlords who had underpaid or not paid income tax, a Freedom of Information request submitted by the Telegraph revealed.
This was a notable 28 per cent increase on the 8,704 caught in 2018.
The tax man launched its Let Property campaign in September 2013 to catch landlords failing to pay their income tax.
Last year, HMRC collected £44.7m in tax, a rise of 36 per cent from £32.8m the year before.
Landlords also coughed up £7.6m in fines for non-payment of income tax, also a 36 per cent rise of the previous year.