Is there an actual law that states that you have to pay income tax?

The movie "Freedom to Fascism" is inaccurate, conspiracy theory nonsense. I suggest you go to http://evans-legal.com/dan/tpfaq.html and lookup almost every point in the film. I also recommend that you try and verify different quotes from the film from RELIABLE websites.

There are income tax laws in the United States. They are codified as Title 26 of the U.S. Code. You can read them at http://www.law.cornell.edu/uscode/26/usc_sup_01_26.html or at http://uscode.house.gov/download/title_26.shtml
It is long and boring reading, but they are all there. The sections that apply to most people are sections 1, 61, 62, 63, 3402, 6011, and 6012. Yes, your wages are income and there is a tax on them.

Title 26 is known as prima facie law or evidence of the actual laws passed by Congress. To read the actual laws passed by Congress, you have to look in the U.S. Statutes at Large. For the most part, these are not available online. However, you can read them at most Federal Depository Libraries(FDL) and many law libraries. You can find an FDL in your state at http://catalog.gpo.gov/fdlpdir/FDLPdir.jsp

Our current tax laws get their structure from the Internal Revenue Act of 1954 and the Tax Reform Act of 1986. The 1954 act can be found in Volume 68A starting on page 3 in the U.S. Statutes at Large. The 1986 act can be found in Volume 100 starting on page 2085. Both laws were passed by Congress and signed into law by a President. Various acts of Congress have modified those two laws throughout the years.

Income taxes are legal under the Constitution because income taxes are INDIRECT taxes in a Constitutional sense. In HYLTON v. U S, 3 U.S. 171 (1796), a Supreme Court that included at least two of the original framers of the Constitution, Justice Samuel Chase stated, "...the direct taxes contemplated by the Constitution, are only two, to wit, a capitation, or poll tax, simply, without regard to property, profession, or any other circumstance; and a tax on LAND."

In 1861, the first income tax law in the U.S. was passed. In Springer v. United States, 102 U.S. 586 (1880) (A Supreme Court case), the court had to consider whether an income tax on an individual was constitutional. The court stated, "Our conclusions are, that direct taxes, within the meaning of the Constitution, are only capitation taxes, as expressed in that instrument, and taxes on real estate; and that the tax of which the plaintiff in error complains is within the category of an excise or duty." Springer was the plaintiff in error. The Supreme Court upheld the constitutionality of the income tax law that was in effect in 1865.

After the ratification of the 16th amendment, the Supreme Court in STANTON v. BALTIC MINING CO, 240 U.S. 103 (1916) stated, "...by the previous ruling it was settled that the provisions of the 16th Amendment conferred no new power of taxation, but simply prohibited the previous COMPLETE AND PLENARY POWER OF INCOME TAXATION POSSESSED BY CONGRESS FROM THE BEGINNING from being taken out of the category of indirect taxation to which it inherently belonged..."

The book, "The Law that Never Was" by Bill Benson has been completed refuted. Also, no court has EVER accepted any of the arguments brought forth in that book. Here is a court case that discussed the book. In U.S. v. Thomas, 788 F.2d 1250 (7th Cir. 1986), cert. den. 107 S.Ct. 187 (1986). You can read it at http://bulk.resource.org/courts.gov/c/F2/788/788.F2d.1250.85-2120.html

The Federal Reserve act was properly passed by Congress and does not require a Constitutional amendment. While the Federal Reserve Act was passed on Dec. 23, 1913, according to the Congressional record, the bill passed the house by a count of 298 to 60. 358 members voted out of 435, that's pretty good attendance. That's probably better attendance than the current House of Representative gets on most days. The Senate passed the bill with a vote of 43 to 25. That's 68 members voted out of 96.

The quote by Woodrow Wilson that the film says he made in 1919 is false. First, there is no record anywhere that Woodrow Wilson said the first part of that quote. The rest of the quote is taken from Woodrow Wilson's book, "The New Freedom". However, "The New Freedom" was published in 1913! Also, the book is actually a compilation of speeches he made on the campaign trail during 1911 and 1912. He was really discussing corporate monopolies and not the Federal Reserve (which didn't exist yet) or the banks. You can read "The New Freedom" for yourself at http://www.gutenberg.org/etext/14811

The Federal Reserve is independently audited every year. Those audits and more are part of the Federal Reserve annual report to Congress.
http://www.federalreserve.gov/boarddocs/rptcongress/annual06/default.htm
http://www.federalreserve.gov/boarddocs/rptcongress/annual06/sec6/c3.htm

Look at all I have written refuting many points in the movie, "Freedom to Fascism" and that's only the first five minutes of it.