The society also achieved record pre-tax profit of £116.6m, increasing from £108m in 2015.
Leeds Building Society increased its gross lending by 28% to £4bn in 2016 with the help of surging buy-to-let lending.
Peter Hill, chief executive of the society, admitted the rush to buy properties before the 3% stamp duty surcharge came into force on March 31 was a factor in surging lending growth.
He said: “March was a massive month for us and that was undoubtedly due to the stamp duty changes but it was a very good year in buy-to-let throughout 2016.
“Buy-to-let remo is a very important sector for us and I expect that market to be quite competitive in 2017.”
The society also achieved record pre-tax profit of £116.6m, increasing from £108m in 2015.
Hill added: “It turned out to be a really good year with a strong increase in business.
“It was funny one because it was a very uncertain year in many respects, with regard to political events for example.”
Hill said the society helped 17,500 borrowers in underserved markets in 2016, which he classed as first-time buyers, shared ownership, affordable housing, Help to Buy and interest-only.
He added that these customer types remain a primary focus for the society.
Leeds will look to attract business this year by widening criteria and quickening up the application process for customers.
For example the lender is looking to streamline how it processes documents for low risk cases.
When asked whether he felt the society could sustain the same levels of profit next year, Hill responded: “The outlook on profit looks more steady than spectacular.
“The low interest rate environment makes it difficult to grow profits.
“However with mutuals the real test is whether you’ve got enough capital to support future growth and we do.”
