ASED Basic Guide http://www.irs.gov/irm/part25/irm_25-006-001r.html#d0e573 http://www.irs.gov/irm/part25/irm_25-006-001r.html#d0e116 Internal Revenue Manual, 25.6.1, Statute of Limitations IRM 25.6.1.5 http://www.irs.gov/irm/part25/irm_25-006-001r.html http://www.irs.gov/irm/part25/irm_25-006-001r.html#d0e116 Statute of Limitations http://www.irs.gov/irm/part25/irm_25-006-001r.html#d0e116 statute of limitations IRS "period of limitations" http://www.irs.gov/irm/part25/irm_25-006-001r.html#d0e116 CSED period of limitations period of limitations