BofI Holding (BOFI) in San Diego earned a record quarterly profit on surging interest income and a higher interest margin.

The holding company for BofI Federal Bank, formerly Bank of Internet, reported Wednesday that it made a $9.8 million profit in the quarter ended Dec. 31, 2012, an increase of 47% from the prior-year period. Per-share earnings of 70 cents met the expectations of analysts polled by Bloomberg.

BofI saw a quarterly jump in both interest and noninterest income, as its total assets rose 29%, to $2.9 billion, on the year. Its loan portfolio grew by $628 million, or 41%, and its deposits grew by $415 million, or 27%, compared to the last quarter of 2011.

Higher interest income and falling expenses boosted the net interest income by 31%, to $25 million, for the quarter. BofI’s provision for loan losses rose 22%, to $2 million, while the ratio of net annualized charge-offs to loans outstanding fell to 0.13% from 0.39%. The bank’s net interest margin widened by 21 basis points, to 3.81%.

Noninterest income rose 109%, to $6.2 million, mostly due to higher gains on mortgage sales. Noninterest expense was $12.7 million, 38% higher than the prior-year period, on higher compensation and advertising costs.