Unless stated otherwise in law, the Statute of Limitations for filing of criminal charges is 5 years from the date of the actions charged, although where specified in law, it can be extended for a predefined time based on the crime and the entity committing a crime. Major Fraud ($1,000,000+) will be extended to 7 years if committed by anyone who is not committing the crime at the behest of a Bank (if you are, this will be extended to 10 years) AND the victim of the fraud is the United States Government. Additionally, if charges are dismissed in court for reasons unrelated to the statute of limitations, the court may grant a sixth month extension from the date of the statute of limitations to refile charges, and may grant an extension at the court's discretion if evidence is in a foreign nation. All if the crime occurs over multiple dates, the date of the last action in the charge will be the start of the Statute of Limitations.
The Federal Government has no statute of limitation for any crime if it is a Capital offense, a terrorist charge, or a sexual offense against a child.
At a state level, this will depend on the states in question.