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How a Later Application Inherits an Earlier One's Date

Written from 35 U.S.C. 120. This is the statute. Current as of 22 August 2026.

What it says

A later application covering an invention the earlier one disclosed, to the section 112(a) standard with best mode carved out, is treated as though filed on the earlier date as to such invention, on three conditions: a common inventor, copendency with the earlier application or one similarly entitled, and a specific reference.

Section 120 is the provision that lets a family of applications share one date. It is why patent families exist in the shape they do.

Three conditions attach. The later application must name at least one common inventor. It must contain a specific reference to the earlier application. And it must be filed before the earlier application is patented, abandoned, or terminated.

That third condition is the one that does the structural work. It is called copendency. The statute lets the chain run through the first application or through "an application similarly entitled to the benefit of the filing date of the first application", so an intermediate continuation can carry it forward. What cannot happen is reconstruction: once every application capable of carrying the benefit has stopped being pending, there is no reaching back.

This is why a family is built forward rather than assembled later, and why the question of what to file next is usually asked while something is still pending rather than after.

What This Does Not Decide

Pendency is a deadline, and a deadline invites a page to tell you when to act. This one describes the condition and stops there. Whether to file a continuation, and when, is a strategy question with consequences that cannot be walked back, and the record for this section names that as its specific risk.
  • It does not advise on whether or when to file a continuation.
  • It does not say whether an earlier disclosure supports a later claim. Like section 119(e), this operates "as to such invention", so a family can hold claims with different effective filing dates.
  • It does not cover what the family costs in term, which is a separate question with its own decisions.

Educational, not legal advice. Filing decisions and benefit claims carry deadlines that do not reopen, which is the practical reason to take them to a registered patent practitioner early.

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