How many years can the internal revenue service collect?

The statute of limitations for IRS is 10 years from the date of assessment of the tax, although it could be extended under certain circumstances.

Six years is correct unless he has entered into an agreement which would toll the statute of limitations .

The IRS generally has 10 years to collect on a tax debt. The 10 years "statute" starts the date the tax debt was assessed, and generally expires after 10 years, unless one of a number of actions occur, such as filing for bankruptcy, filing an Offer in Compromise, requesting a Collection Due Process Hearing, etc., which may "pause" the statute. The 10 year statute is called the Collection Statute Expiration Date, or "CSED". A tax attorney could investigate and give you the CSEDs for each tax year that has a balance, so that you know how long the IRS could legally collect on each tax liability.

The I.R.S. has 10 years from the date of assessment to collect the tax owed. Note that this is from the date of assessment, and not from the date of the filing of the return or the tax year involved. So, for instance, if you file your tax return for tax year 2002 on April 15, 2003, then the I.R.S. would have 10 years from that date to collect any amount you show as being owed. However, if the I.R.S. conducts an audit on your return and changes the assessed balance for 2002 on August 28, 2005, then the 10 year period would be from that assessment date (August 28, 2015). Additionally, some actions can extend the period that the I.R.S. has to collect. If you file an appeal with an I.R.S. appeals officer, for example, the 10 year period is put on hold until that appeal is handled. So if your case is in appeals for a 6 month period, then another 6 months is tacked onto the 10 year period. You can contact the I.R.S. to get a CSED (collection statute expiration date) for any tax period that you owe. This will let you know exactly how long the I.R.S. has left to collect on any particular tax year(s) for which you are making payments.

The IRS generally has 10 years to collect taxes or file liens from the time that the tax is assessed. This period can be suspended in certain instances if the IRS is prohibited from taking collection action, such as during a pending taxpayer due process hearing.