Subchapter A — Limitations on Assessment and Collection (Sections 6501 to 6504)
Subchapter B — Limitations on Credit or Refund (Sections 6511 to 6515)
Subchapter C — Mitigation of Effect of Period of Limitations (Section 6521)
Subchapter D — Periods of Limitation in Judicial Proceedings (Sections 6531 to 6533)