How far back can IRS collect a debt?
They can go back three years or more in order to audit your tax returns. If you owe a back tax bill, they will charge you for it and if they owe you a refund, you should claim it before three years is over. Check out http://www.ehow.com/about_5074887_far-back-irs-back-taxes.html for more information.
The IRS has 3 years to audit your tax return or to assess any additional tax liabilities, 10 years to collect outstanding tax liabilities. So if they know you owe them they have ten years to collect.
The IRS can audit you for up to the past seven years. Now here is the tricky part....if it has been established that the IRS is owed money, I believe that there is no time frame to collect.