The figures come after a freedom of information request to the HRMC submitted by Brian Hall, a consultant who has written a new buy-to-let index.
He said the total net value of housing benefit and income tax breaks to private landlords is around £9bn per annum and rising.
And he suggested that based on DCLG figures the private rented sector benefited from circa £6.2bn in housing benefits in 2010/11.
Overall buy-to-let profitability fell again this quarter for both geared and cash investors, said Hall.
His latest buy-to-let index research claimed over a short investment period of five years, costs and falling property prices outstripped rental yield surpluses and resulted in losses for geared investors, with interest-only landlords experiencing a 68% loss and repayment landlords experiencing a 67% loss.
Over the same period, a cash investor would break even, once opportunity costs are taken into account.
Hall said: "The most recent IMF report suggests that property prices are still overvalued by up to 15%. Investors need to consider gearing, property prices and factors like opportunity costs, interest rates, voids and arrears rates and management costs when calculating profitability."
