The lending group, which owns mortgage brands including Precise, Kent Reliance, Rely, Charter Savings Bank, Interbay and Heritable, recorded growth of 3.2% in its net loan book, which reached £25.9bn.

It says that loan book growth was supported by a 19% increase in originations to £4.7bn and its ongoing focus on diversification into higher-yielding areas of the market.

The fall in its pre-tax profits related to an impairment charge in 2025, whereas in 2024 the group received a credit back after a previous impairment.

This was partially offset by an increase in net interest income, a gain on sale of the second charge mortgage portfolio and an increase in commissions and servicing fees income, OSB says.

In September 2025, OSB sold its second charge mortgage portfolio for £134.2m, which translated to a profit of £3.4m.

In December 2024, the securitised £1.25bn of buy-to-let mortgages, which resulted in a loss on the sale of £2.4m from this transaction.

Chief executive Andy Golding says: “The Group delivered resilient financial performance in the first year of the transition period, which was in line with our 2025 guidance.

“We also made tangible progress against our strategy that we set out at the Investor update last year.

“The loan book diversification has been gaining momentum and in 2025, combined originations in our higher-yielding sub-segments grew by 53%.

“The buy-to-let gross loan book represented 68% of the group’s total gross loan book, a reduction from 70% a year ago, on track with our 2029 target.

“Finally, many milestones were achieved in the transformation programme in the year.

“I am particularly pleased with the launch of our new lending platform, a new brand dedicated to buy-to-let borrowers: Rely, as well as a successful migration of some of our existing savers onto the new savings platform.

“All this was achieved on time and to budget.”