An IRS tax lien is a judgement placed on your credit report that usually follows to any real estate that you own by also being placed in a county courthouse.
The IRS usually files a lien when:
1. You owe a lot of money usually north of $25,000 and have been unresponsive at communicating with them.
2. Your case has been determined to be "Currently Not collectible" (CNC) whereas the IRS chooses not to actively collect against you but wants to protect their interest.
3. You file an Offer in Compromise (OIC) with the IRS and the IRS places the lien on you in advance of acceptance, removing the lien once your Offer is accepted and paid.
Telemarketers and tax lien mailers get a hold of this lien info and
1. Call you (often excessively)
2. Send out mailings that often look like IRS correspondence.
Sometimes these folks are misleading just to make some kind of sale. If you are CNC or OIC above - you can usually ignore these folks - why mess with the resolution of your case.
How can you get a Tax Lien removed? Read how HERE.