The period of validity of a registered trademark is 10 year. Where it is necessary to continue to use a registered trademark after its expiration, it shall apply for renewal of registration within 6 months before its expiration. If the application cannot be submitted within this period, there will be a grace period of 6 months. If no application is filed within the grace period, the Trademark Office will revoke it after the expiration. An application for renewal of a registered trademark may be entrusted to a trademark agency recognized by the state. Should be submitted: (1) trademark renewal registration application, trademark agency power of attorney-made by the firm; (2) A copy of the applicant's ID card or business license and a copy of the registration certificate-provided by the applicant; (3) If the company's name or address is changed, the original certificate of change issued by the Industrial and Commercial Bureau shall also be provided.