However, many buy-to-let investors do not understand the tax implications of changing property ownership, according to the research on behalf of specialist lender Kent Reliance.
Landlords have now been urged to plan for tax changes on mortgage interest, as relief is gradually knocked down to the basic rate by 2020.
Kent Reliance data showed a surge in limited company lending last year, with seven in 10 buy-to-let applications for house purchase via limited company during the first three quarters of 2017, up from 45% in 2016 as a whole.
On top of the fifth who have already transferred property ownership, a further one in six landlords plan to make a similar move in the future, the research showed.
However, there are differing attitudes over the benefits of such a move.
More than half of smaller landlords say changing ownership is not worthwhile, while just a quarter of larger professional landlords say the same.
Adrian Moloney, sales and marketing director at OneSavings Bank, said: “Landlords have had nearly three years to understand and prepare for the changes to the tax treatment of mortgage interest.
“Most have risen to the challenge, but a few might have quite the shock when they come to file this year’s tax return.
“As the tax year draws to a close, brokers can use this opportunity to engage with their clients, and make sure they’re aware of the potential impact on their finances.
“Many landlords have sought to move to a limited company structure, or transferred ownership to a spouse but it’s not a one-size-fits-all solution so it’s vital that landlords affected seek professional tax advice.”