The Clock You Did Not Know You Were Running: Patent Term Adjustment, Extension, Terminal Disclaimers, and Double Patenting
By Casey Scott McKay ·
Patent term looks like a simple arithmetic problem and is not. This article separates the four mechanisms that determine when a patent actually expires - the twenty-year measure from the earliest non-provisional filing, adjustment for office delay, extension for regulatory review, and the terminal disclaimers that surrender term voluntarily. It explains how adjustment is calculated, where applicant conduct reduces it, and why the overlap rule matters. It works obviousness-type double patenting as the doctrine that reaches across a family, the terminal disclaimer that cures it at the cost of common ownership and aligned expiration, and the Section 121 safe harbor that only protects divisionals filed as a consequence of a restriction requirement. It then covers what In re Cellect and Allergan v. MSN changed, and closes with the audit worth running on any family with a term that matters.
IP and Technology > Patent Counseling Transactions | Article | Published 2 June 2025 - Updated 3 December 2025 | Casey Scott McKay - marksy.us
Summary. Patent term looks like a simple arithmetic problem and is not. This article separates the four mechanisms that determine when a patent actually expires — the twenty-year measure from the earliest non-provisional filing, adjustment for office delay, extension for regulatory review, and the terminal disclaimers that surrender term voluntarily. It explains how adjustment is calculated, where applicant conduct reduces it, and why the overlap rule matters. It works obviousness-type double patenting as the doctrine that reaches across a family, the terminal disclaimer that cures it at the cost of common ownership and aligned expiration, and the Section 121 safe harbor that only protects divisionals filed as a consequence of a restriction requirement. It then covers what In re Cellect and Allergan v. MSN changed, and closes with the audit worth running on any family with a term that matters.
Keywords: patent term · twenty years from filing · patent term adjustment · A delay B delay C delay · applicant delay reduction · overlap rule · Wyeth · patent term extension · regulatory review period · obviousness type double patenting · Gilead · In re Cellect · Allergan v MSN · terminal disclaimer · common ownership requirement · Section 121 safe harbor · restriction requirement · family expiration alignment · continuation strategy · term audit
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