As of September 30, 2012, the tax debt of individuals and businesses that owed the U.S. government was about $364 billion, according to the IRS.The tax-debt inventory is the sum of all taxes owed to the IRS at a particular point in time, including debts from the current year and debts from previous years that fall within the 10-year statute of limitations on collections. The inventory of tax debts comprises tax assessments that are not collected along with related penalty and interest charges. Federal taxes that are owed become tax debts when the tax is assessed but not paid. Millions of individual and business taxpayers owe billions of dollars in unpaid federal tax debts, and the IRS expends substantial resources trying to collect these debts.