Filing the provisional specification is an optional step, if you already have complete information about your invention, then you can directly go for complete specification, there is no requirement to file the provisional application for patent.
How does a patent expire?
- The patent expires if it has lived its full term i.e. 20 years
2. The patentee fails to pay the annual renewal fee.
3. The validity of the patent has been successfully challenged by an opponent by filing an opposition.
4. The patent is revoked.