Bush-era tax cuts: If Congress does nothing, the 2001, 2003 and 2006 tax cuts will expire at the end of December 2012.
If they do expire, most Americans' tax bills would go up and the surge of additional revenue into federal coffers would greatly improve the deficit picture over the next decade.
But many worry the overnight jump in taxes could hurt the economy if it's still weak. And others say higher rates across the board is not the most efficient way of reducing deficits.
In any case, most Republicans want to make the tax cuts permanent while many Democrats want to make them permanent for everyone except high-income households.
If all the cuts are extended, they could reduce revenues by an estimated $3.7 trillion over a decade. If only most of them are extended, that would reduce revenues by about $3 trillion.