To maintain a patent in a country, annuity fees or maintenance fees must be timely paid.  If these fees are not paid, the patent will expire.  Some countries require these fees to be paid beginning at a specific date from the filing date or priority date.  Some countries require fees to be paid annually throughout the life of the patent. Some countries requires the fee to be paid every four years. Some countries require a fee once at the five or ten year anniversary date.  The rules that govern how the fees are paid, who can pay these fees, what is window period for paying these fee, what is last date for payment also varies from country to country.   If the fee is not timely paid, some countries allow late payment (along with surcharge) if submitted within a renewal period.  

​

​