After your tax liability is assessed, the IRS has 10 years to collect. This is known as the Collection Statute Expiration Date (CSED).
There have been cases where the collection statute has been renewed for well beyond 10 years, so it is important that you keep the following items on hand:
All of your tax records (both electronic and hard copies)
Proof of when your return was mailed or filed
Pertinent receipts as they relate to the basis in assets