This week marks the deadline to raise the U.S. debt ceiling.

With the U.S. Congress still in negotiations, the consequences could be dire if the largest economy on earth can’t pay the bills.

The U.S. bridges the gap between money spent and taxes collected by selling Treasury bonds to investors, such as China. If the U.S. defaults, it would stop paying money it owed to these bond holders.

Without a deal, world markets could stumble into a recession because these bonds would lose value.

No one can say exactly what happens when the money runs out—but the uncertainty alone is harmful. Money is raised through tax receipts, but only to pay the interest on bonds already issued.

Learn more here: http://www.bbc.co.uk/news/business-24453400