What can happen if patent maintenance fees are not paid?

When patent maintenance fees are not paid, the patent may be abandoned or expire. Patent maintenance fees are required at regular intervals to keep a granted patent in force. If these fees are not paid within the specified time frame, the patent office considers the patent abandoned, and it will no longer hold legal protection. This means that others can freely use, make, sell, or distribute the invention without any infringement consequences.

While the other choices could seem relevant, they do not accurately represent the consequences of not paying maintenance fees. For example, a patent cannot automatically be extended without the necessary actions taken by the patent holder, and the rights to refile are not typically affected by the maintenance fee status but rather by other factors like prior disclosures. Additionally, while failing to pay fees does make the patent available for others to use after abandonment or expiration, it is not the primary outcome; hence the focus is on the abandonment or expiration itself.