Most people would agree that for horrendous crimes there should be no statute of limitations for prosecution. For example, the federal government and most states impose no statute of limitations on murder charges. But in the case of sexual assault, state laws dictate varying statutes of limitations. When it comes to tax fraud, the statute of limitations is usually three years from when the tax return was filed, but it can be extended to six years if the person omitted more than 25% of their income.