What can I do if my fiance told me I have a warrant from the IRS?

It is very rare that the I.R.S. will issue a warrant for anyone's arrest. Although there are some tax issues which can escalate to criminal charges, most do not. The fact of the matter is that if a taxpayer owes the I.R.S. money, they'd much rather work to collect the money civilly than to attempt to charge the person criminally; throwing someone in jail is not going to pay the debt owed to the I.R.S. In all likelihood, if the I.R.S. is holding you responsible for some action, you would have received mailed correspondence from them first. If you have moved since your last tax return, then the I.R.S. may have sent notices to an old address. If you really want to clear this issue up, then you may want to call your local I.R.S. service center (http://www.irs.gov/localcontacts/article/0,,id=98236,00.html) and ask them to review your account to see if any notices have been sent, or if there is any other activity on your account. If they want to know why you're calling, then you can simply state that your former fianc? has implied that he has filed a false tax-related report against you, that he has stated that the police are now involved, and that you wanted to check directly with the source to see if any of this was true. If you find that the I.R.S. is in fact reviewing your account for some reason, then you may wish to speak with a tax attorney regarding how to best respond to the I.R.S.'s inquiries, and what documentation or information would be pertinent for defending yourself against any claims.