Priority Dates

In one line

Every claim in a specification has its own priority date, and it is the date of the earliest document that fairly supports it.

In the wording a student can write in an exam: section 11(1) of the Patents Act, 1970 provides that there shall be a priority date for each claim of a complete specification, and sub-sections (2) to (7) fix that date by reference to the earlier specification on which the claim is fairly based.

Why priority is per claim and not per patent

Because a specification is written over time. A provisional in March, a second provisional in July, a complete specification the following February: each adds something, and the claims that rest on the March document deserve the March date while the claims that rest only on the February document cannot have it.

And because prior art is judged at the priority date. Chapter 400 works the state of the art. A document published in October is prior art against a claim with a February date and not against one with a March date. So a single patent can be valid in part and invalid in part, and section 114 gives relief for infringement of a partially valid specification, which chapter 1110 works.

The provision itself

Section 11(1). There shall be a priority date for each claim of a complete specification.

Section 11(2). Where a complete specification is filed in pursuance of a single application accompanied by a provisional specification, or by a specification treated as provisional under section 9(3), and the claim is fairly based on the matter disclosed in that specification, the priority date of that claim shall be the date of filing of the relevant specification.

Section 11(3). Where the complete specification is filed or proceeded with in pursuance of two or more applications accompanied by such specifications, and the claim is fairly based on the matter disclosed (a) in one of those specifications, the priority date is the date of filing of the application accompanied by that specification; (b) partly in one and partly in another, the priority date is the date of filing of the application accompanied by the specification of the later date.

Section 11(3A), inserted in 2005. Where a complete specification based on a previously filed application in India has been filed within twelve months from the date of that application, and the claim is fairly based on the matter disclosed in the previously filed application, the priority date of that claim shall be the date of the previously filed application in which the matter was first disclosed.

Section 11(4). Where the complete specification has been filed in pursuance of a further application under section 16, and the claim is fairly based on the matter disclosed in any of the earlier specifications, provisional or complete, the priority date shall be the date of filing of the specification in which the matter was first disclosed.