Interest income on securities purchased in open-market operations, including Treasurys, government-sponsored enterprise debt and mortgage-backed securities, rose to $90.4 billion, an increase of $9.9 billion over the previous year, the Fed said today in its 2013 combined annual financial statements released in Washington.

After paying for its own expenses and making capital adjustments, the Fed returns the remainder of its earnings to U.S. taxpayers. Remittances to the federal government are continuing as policy makers press on with their quantitative easing program, in which the Fed buys bonds to reduce lending costs to support the economy and boost hiring.

The large-scale asset purchases increased total assets held by the Fed by $1.1 trillion last year to $4 trillion as of Dec. 31. The balance sheet this week rose to a record $4.18 trillion, according to a report released Thursday.

The policy-setting Federal Open Market Committee has pared the pace of monthly bond buying to $65 billion a month from $85 billion in December. The FOMC meets again next week.

Interest income from Treasury securities rose to $51.6 billion last year from $46.4 billion in 2012, while interest on mortgage-backed securities increased to $36.6 billion from $31.4 billion, the Fed said today.

The central bank provided the figure as part of its annual audited financial statements.