The number of landlords in the UK has jumped by 7% over the last year to reach 1,750,000, according to HMRC data on those who declared income from property.
The official data extends only to April 2014, giving rise to the expectation that the current figure is likely to be higher still after the recent race to acquire buy-to-let properties before the start of the new stamp duty regime.
The speedy surge in buy-to-let has also been fuelled by cheap mortgages, low interest on savings and rising rents.
Landlords banked a total of £14.2bn in net income from their rental properties during the year, up from £13.1bn the year before when there were 1,630,000 landlords.
The new stamp duty added a 3% surcharge on second homes. From 2017, mortgage repayment relief will start gradually to be withdrawn.
These measures could dampen the buy-to-let market which until now has been attractive for its returns.
