The federal deficit ran $62 billion in August, the Congressional Budget Office estimated Tuesday, bringing the total deficit through the first 11 months of fiscal 2015 to $528 billion.

Compared with a year earlier, the deficit has dropped by $61 billion, although that number reflects some shifts in the timing of expenditures.

The Congressional Budget Office, Congress' in-house budget and economic projection agency, sees the total deficit for fiscal 2015, which ends Sept. 30, totaling $426 billion. That would be the lowest annual deficit of President Obama's tenure.

The annual deficit has improved so far this year because tax receipts are growing faster than spending.

Total receipts were up by 8 percent through the first 11 months, according to the Congressional Budget Office, driven primarily by growing withholdings from workers' paychecks.

Government spending was up 5 percent. Part of the increase in expenditures was the result of the growing costs of healthcare insurance provided by the government through Medicare and Medicaid. Bailed-out mortgage giants Fannie Mae and Freddie Mac also made $54 billion less in payments to the government, a development that shows up as increased spending in the government's accounting measures. A $23 billion write-down on the government's portfolio of student loans also added to spending.

If the budget office's projection for this year's deficit is correct, it will be the smallest annual shortfall since 2007, the year before the financial crisis sent deficits soaring above the $1 trillion mark.

The budget office sees the deficit shrinking again in fiscal 2016 as the economy continues to improve. But then annual shortfalls are expected to begin growing again, driven largely by spending on entitlement programs for seniors, until again reaching $1 trillion by the end of the next decade.

Over that period, the debt, which represents the accrued annual deficits, is also projected to dip slightly from its current 74 percent of economic output and begin rising toward 77 percent.