When do I have to pay annual fees in Korea?

In Korea the annual fees for the first three years have to be paid in a lump sum within three months as from the grant decision. Subsequent annual fees are payable yearly in advance. For patents granted up to June 1997 (pre-grant opposition system), annual fees are due for each year as from the date of publication of the examined document. For those granted from July 1997 onwards (post-grant opposition system), they are due on the anniversary of the first payment.