If you're unable to pay off your federal taxes due to a serious illness, natural disaster, and other hardship, call the IRS at 1-800-829-1040 or visit your local IRS officeÂ as soon as you can to explain your situation.
The IRS will work with you to come up with a solution.
For outstanding state taxes, contact your state tax agency to explore alternative payment options.
Whatever you do, don't ignore the problem, hoping it'll go away. It won't. The sooner you address it, the easier it will be to resolve.
See also the IRS video series Owe Taxes? Understanding IRS Collection Efforts.