Estimates of financial subsidies to individual owner occupiers, by way of mortgage interest tax relief and non taxation of imputed rent, are shown to vary, depending upon the data source or sampling frame used. Subsidy estimates based upon building society data are significantly higher than those derived from a random sample of owner occupier households. While the incidence of subsidy increases with income and house prices, the level of MlRAS subsidy has fallen over time: households in 1988 only recieved 65070 of the 1985 subsidy in real terms.