The country's legal borrowing limit is currently set at $16.699 trillion.
That level was reached in mid-May. And the Treasury Department began its official juggling act, employing "extraordinary measures" to keep the country from breaching the ceiling. But Treasury doesn't expect those measures to last beyond the middle of October.
Why does it need to be raised at all? Both parties in Congress have approved permanent tax cuts and spending increases over the years.
By doing so, they add to future deficits and increase the country's borrowing needs. Raising the ceiling simply lets Treasury continue to pay all the country's obligations that Congress has already approved -- whether it's a payment to a federal contractor, a Social Security check to a senior, or interest on the debt to a bond investor.
What's more, the aging population means there will be more spending on Medicare and Social Security with each passing year.
That's why raising the debt ceiling is not a "license to spend more," as some Republicans assert. And it's why the debt ceiling always needs to be raised periodically. Over the past two decades, it's been raised about 15 times.
What happens if the debt ceiling isn't raised? Uncle Sam would still have revenue coming in to pay for government services and agencies. Just not enough to pay for everything. And the longer the debt ceiling crisis lasts, the harder it would be to keep government operations running.
"After two weeks you'd have absolute paralysis," said Steve Bell, economic policy director at the Bipartisan Policy Center.
More problematic: The country could no longer pay all of its bills in full and on time. Treasury then would have to make legally murky decisions about who to pay and who to stiff.
Even if bond investors continue to be paid on time, the country could still be perceived as in default if it fails to pay its other legal obligations.
And if the full faith and credit of the United States is called into question, that could be disastrous for markets and interest rates -- which would harm the U.S. economy and Americans' financial well being.