The most profitable bank in the land isn’t on Wall Street; it’s on Constitution Avenue.

The Federal Reserve on Thursday announced record earnings of $91 billion, easily trouncing any private bank. Of that total, $89 billion was passed along to the U.S. treasury, improving the nation’s fiscal health.

The profits came about overwhelmingly due to the Fed’s four-year effort to pump money into the U.S. economy by buying longer-term bonds. The $2.7 trillion and counting in Treasury and mortgage-related securities on the Fed’s books all pay a yield, and that interest income is the primary driver of the Federal Reserve system’s revenue—that alone accounted for $80.5 billion. The Fed also earned $6.1 billion from selling off assets acquired as part of the central bank’s financial crisis response, and $450 million in fees for services  provided by reserve banks, such as for clearing checks.

The central bank then subtracts all its operating expenses, such as for buildings and employee salaries, and refunds the money left over to taxpayers. The $89 billion refunded to taxpayers is the highest ever, topping the $79.3 billion in 2010 and $75.4 billion in 2011.

It is a nice reminder that the Fed’s unconventional efforts to ease monetary policy, which currently include buying $85 billion in securities each month, are not the same as spending taxpayer money; rather, the Fed is buying assets that can actually create a return. At the same time, taxpayers could still end up losing money on the transactions. If interest rates rise significantly in the future, and the Fed sells off the assets to try to stem inflation, the Fed could end up taking a loss.

But for now, it turns out that printing money is a highly profitable business.