The specialist lending group revealed that it will require landlords with four or more managed properties to provide a business plan, assets and liabilities statement and cash flow statement alongside any mortgage application.
Alongside this, borrowers will have to provide details of their wider portfolio.
OneSavings Bank said that brokers will be able to submit information via a new Buy to Let Hub, which has been developed alongside eTech and provides a dashboard which should streamline portfolio stress testing and income coverage ratio assessment.
Portfolio landlords will be subject to an interest rate stress test of 5% on the rest of their portfolio and must meet or exceed an interest cover ratio of 125%.
Adrian Moloney, sales director of OneSavings Bank, said the firm welcomed portfolio landlords and was determined to keep things simple for intermediaries.
He continued: “We’ve chosen to announce our criteria well ahead of the October deadline to help brokers prepare for the changes in good time so they can feel confident when preparing clients to submit a portfolio application.
“Together with the new Buy to Let Hub, we’re doing all we can to transition brokers and their clients into the new landscape with the minimum of fuss,” he added.