WASHINGTON—Decrying the traditional filing season as “an irredeemable heresy,” an Internal Revenue Service splinter group demanded Wednesday that taxpayers recognize Aug. 15 as the one true tax day. “Any righteous interpretation of the 16th Amendment and the original Revenue Act of 1913 makes clear that Apr. 15 is not the sanctified deadline for payment of income tax,” read an excerpt from a manifesto by the IRS Fundamentalists, a radicalized group that seeks to restore what it views as the purity of the U.S. tax code and has threatened to carry out vigilante audits of anyone who does not file on Aug. 15 of this year. “You have been led astray by the false shepherds of TaxAct and H&R Block, who seek to deceive and destroy you. Only by postmarking your federal return by Aug. 15 and enclosing a check for the amount due (if any) can you fulfill your sacred obligation as a U.S. taxpayer.” At press time, the FBI had reportedly raided an IRS Fundamentalist compound at which members were allegedly rigging blue mail collection boxes to explode if anyone attempted to mail in their taxes on Apr. 15.