The IRS collection statute runs 10 years from the date your tax is "assessed." The collection statute can be tolled in certain situations (e.g., bankruptcy). The IRS might have written off the balance you owed if the collection statute (CSED) expired. You should request copies of your account transcripts from the IRS for the tax years that you owe(d). The IRS generally inputs the term "write-off" if the CSED has expired.
If you stop paying one of two things could occur. If you don't owe the tax, then the IRS will do nothing. Of course they will continue to accept your payments even they no longer can take collection action against you. Second, the collection statute of limitations might not have expired. If you do still owe the tax, then defaulting will put you back into collection status and will expose you to IRS levies, wage garnishments, and seizures.
Get copies of your account transcripts and look for the term "write off". You might even be able to get a hold of someone at the IRS who can advise on the CSED.
This material does not constitute tax, legal or accounting advice. It was not intended or written for use and cannot be used by any taxpayer for the purpose of avoiding any IRS or NYS penalty. The information contained herein is for informational purposes only as a service to the public, and is not legal advice or a substitute for legal counsel, nor does it constitute advertising or a solicitation. This response is not intended to create, and does not create, an attorney-client relationship between you and the author.
The other answer gives you the info you need. Call and ask about the transcript. I have actually had them answer the question about the CSED as that is not private.
This is not legal advice nor intended to create an attorney-client relationship. The information provided here is informational in nature only. This attorney may not be licensed in the jurisdiction which you have a question about so the answer could be only general in nature. Visit Steve Zelinger's website: http://www.stevenzelinger.com/
The best choice is to retain a tax attorney. Certain appeals, request for an Offer In Compromise, bankruptcy and a consent can extend the statute of limitations. It would be well worth having a tax attorney represent you, look at the transcript and see exactly where you are.
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.