When to file a patent?

In almost every country, patent rights are lost when the invention is sold or publicly disclosed unless a patent application has already been filed. A notable exception is the United States, where the inventor can publicly disclose the invention and then file a corresponding patent application within one year, without losing patent rights. However, in this scenario you would still lose your patent rights essentially everywhere else. Therefore, the best time to file a patent application is before any publication disclosure of the invention. Filing an application in just one country, or filing an international umbrella application under the Patent Cooperation Treaty, is sufficient to preserve your rights in most other countries for at least a year.