In ordinary domestic US utility patent practice, every practitioner is accustomed to the fact that you can get away with filing your patent application with informal drawings. And later when you get around to it, you can prepare formal drawings and file them in your application and it will almost never be a problem.
As I discuss at some length in this blog post, it is the exact opposite situation with PCT applications. The general rule is that if you try to hand in formal drawings after filing day in a PCT application, you will not succeed.
What should practitioners keep in mind about formal and informal drawings so far as PCT applications are concerned? Continue reading