35 U.S.C. § 120 — Benefit of earlier filing date in the United States

This section lets a new patent application get an earlier filing date, borrowed from an earlier application, for the same invention. To qualify: the invention must have already been disclosed — in the way required by section 112(a), except that section's "best mode" requirement doesn't have to be met — in an application filed earlier in the United States (or as allowed under sections 363 or 385). The earlier application must name the same inventor or a joint inventor as the new one. If all this is true, the new application is treated, for that invention, as if it had been filed on the earlier application's filing date. Two more conditions apply. First, the new application must be filed before the earlier application is patented, abandoned, or otherwise finished — or before an application that already carries forward that same earlier filing date is finished. Second, the new application must contain, or be amended to contain, a specific reference back to the earlier application. That specific reference is required: an application only gets this earlier-filing-date benefit if an amendment adding the reference is submitted while the application is still pending, within whatever time the Director of the Patent and Trademark Office requires. If the applicant misses that deadline, the Director may treat it as a waiver — meaning the applicant gives up the right to the earlier filing date. The Director can also set up procedures — which may include paying the fee described in section 41(a)(7) — to let someone submit that reference late, if the delay was unintentional.