A special statute of limitations applicable to tax offenses is found in 26 U.S.C. § 6531. It provides in part that, if a "complaint is instituted" within the limitations period prescribed, i.e., either three years or six years, depending on the type of internal revenue offense, then "the time shall be extended until the date which is nine months after the date of the making of the complaint." The courts have ruled that, in order to toll the statute of limitations, the complaint must be valid, i.e., it must establish probable cause to believe the accused committed an offense. See Jaber v. United States, 381 U.S. 214 (1965); United States v. Bland, 458 F.2d 1, 3-6 (5th Cir. 1972), cert. denied, 409 U.S. 843 (1972); United States v. Miller, 491 F.2d 638, 644-45 (5th Cir.), cert. denied, 419 U.S. 970 (1974).
Aside from continuing offenses and the application of special provisions suspending the running of the statute of limitations (e.g., when a person is a fugitive), statutes of limitations normally begin to run when the offense is complete. In the internal revenue statute, however, Congress has provided that, in the case when a tax return is filed or a tax is paid before the statutory deadline, the limitations period begins to run on the date when the return or payment was due (without regard to any extension of time obtained by the taxpayer). See 26 U.S.C. §§ 6531 and 6513. These statutes are based on the desirability, for purposes of administrative convenience in criminal tax investigations, of a uniform expiration date for most taxpayers despite variations in the dates of actual filing. But see United States v. Habig, 390 U.S. 222, 225, 226 (1968). Habig held that, where an extension of time is secured but the return is filed after the original statutory due date, the period of limitations starts to run when the return is filed rather than on the date (but for the extension) when it was due. Otherwise, the limitation period would begin before the offense was even committed.