It sounds like the confusion is for different tax years. The lien may be for some of the tax years, not the entire balance. The reason the IRS is contacting you is you may be close to the expiration of the statute of limitations.
You need a tax attorney to negotiate with the IRS, get a transcript and help you either get into uncollectible status or set-up an installment agreement.
I hope this helps!
If you do not like this answer or disagree, please look at one of the other answers provided. It is not necessary for you to try prove this answer is "wrong" or something with which you do not agree. This is a free service for you based on limited facts. Nevertheless, many times you need to consult an attorney with the details to get actual advice specific to your concerns. Do not put too many details in your questions or comments because this makes the information public and could hurt you. Government Regulations contained in IRS Circular 230 regulate written communications about Federal tax matters, including e-mail, between us and our clients. This is another attempt by the government to limit your rights and to extend the control of government over individuals and businesses. Nevertheless, such communications are either opinions or other written communications. This is not an opinion. It is other written communication and was not written to be relied upon, by itself, to avoid any tax penalties. In order to receive assurances of protection from tax penalties from a written communication, you should get an opinion letter. If you would like to discuss an opinion letter relating to any matter, please contact me and I will explain what is involved and what it will cost.
If the communications from the IRS give you the contact information for a revenue officer with whom you can have a conversation, then by all means talk to the RO and try to clear this up. Otherwise you should talk to a competent CPA or tax lawyer who can help short-circuit this process for you If you truly can't pay this amount, then you should consider submitting an offer in compromise. Just Google "offer in compromise" and the required paperwork will show up. Given the amount that you may owe - $9,000 - I would try to handle the OIC on my own if I were you.