I personally beat them with facts. Haven't heard from them in almost a year.

To whom it may concern,
I am still waiting for my FOIA request on which I have asked your agency to provide the specific records on which your agency is using to substantiate and justify your claim that I owe these taxes.

The Supreme Court makes it very clear of what the definition of Income is:
Doyle v. Mitchell Bros. Co. 247 U.S. 179 (1918) This case concerns the Corporation Excise Tax Act of August 5, 1909. The court stated: An examination of these and other provisions of the act makes it plain that the legislative purpose was not to tax property as such, or the mere conversion of property (into cash), but to tax the conduct of the business of corporations organized for profit by a measure of the gainful returns from their business operations and property from the time the act took effect. As was pointed out in Flint v. Stone Tracy the tax was imposed 'not upon the franchises of the corporation irrespective of their use in business, nor upon the property of the corporation, but upon the doing of corporate or insurance business and with respect to the carrying on thereof'; an exposition that has been consistently adhered to.

Pollock v. Farmers' Loan & Trust Co. (rehearing) 158 U.S. 601 (1895) "As heretofore stated, the Constitution divided Federal taxation into two great classes, the class of direct taxes, and the class of duties, imposts, and excises; and prescribed two rules which qualified the grant of power as to each class. The power to lay direct taxes apportioned among the states in proportion to their representation in the popular branch of Congress, a representation based on population as ascertained by the census, was plenary and absolute; but to lay direct taxes without apportionment was forbidden." (pg. 617, 618)

Pollock v. Farmer's Loan & Trust Co. 158 U.S. 601 (rehearing) (1895) "It is said that a tax on the whole income of property is not a direct tax in the meaning of the Constitution, but a duty, and, as a duty, leviable without apportionment, whether direct or indirect. We do not think so. Direct taxation was not restricted in one breath, and the restriction blown to the winds in another. (pg 622)
The power to tax real and personal property (labor) and the income from both, there being an apportionment, is conceded: that such a tax is a direct tax in the meaning of the Constitution has not been, and, in our judgment, cannot be successfully denied: . . . (pg 634)
We have considered the act only in respect of the tax on income received from real estate, and from invested personal property, and have not commented on so much of it as bears on gains or profits from business, privileges, or employments, in view of the instances in which taxation on business, privileges, or employments has assumed the guise of an excise tax and been sustained as such. (pg. 635)
Our conclusion may, therefore be summed up as follows:
First. We adhere to the opinion already announced, that, taxes on real estate being indisputably direct taxes, taxes on the rents or income of real estate are equally direct taxes.
Second. We are of the opinion that taxes on personal property or on the income of personal property (labor), are likewise direct taxes.
Third. The tax imposed by sections twenty-seven to thirty-seven, inclusive, of the act of 1894, so far as it falls on the income of real estate and of personal property, being a direct tax within the meaning of the Constitution, and, therefore, unconstitutional and void because not apportioned according to representation, all those sections, constituting one entire scheme of taxation, are necessarily invalid." (pg 637)
Brushaber v. Union Pacific Railroad Co. 240 U.S. 1, 16-17 (1916) "The conclusion reached in the Pollock case ...recognized the fact that taxation on income was, in its nature, an excise, entitled to be enforced as such."

Black's Law Dictionary. 6th Edition.
Excise tax. A tax imposed on the performance of an act, the engaging in an occupation, or the enjoyment of a privilege.

Senator Daniel Inouye from the United States Senate and the Congressional Research Service on June 26th, 1989 clearly stated in a letter to a Mr. Fred Ortiz, tax consultant from Hawaii, and I quote
“I am writing in further response to your inquiry regarding the precise provisions of the Internal Revenue Code (IRS [sic]) that render an individual liable for income taxes.
Based on the research performed by the Congressional Research Service, there is no provision which specifically and unequivocally requires an individual to pay income taxes."
Former IRS director Steve Miller, admitted in a Congressional hearing in May 2013, and I quote “taxes collected by the IRS are not mandatory, but voluntary”.
Miller told House Representative Devin Nunes that “America’s tax system is ‘voluntary’”. When Nunes remarked for clarification that the US tax code is a “voluntary system”, Miller said, “Agreed.”
House Representative Xavier Becerra commented that the ruse of the IRS is kept as a public confidence in the system scheme to keep Americans paying money to the IRS.

We can go on and on. Please answer my FOIA request ASAP.