Seize the Day
Although a motto may appear in the illustration on a Letters Patent granting armorial bearings from the College of Arms in London, it is not mentioned in the text and is not granted. An English armiger my change his/her motto as it takes his/her fancy.
However, in Scotland the motto does appear in the text of a Grant of Arms and is therefore part of the grant.
"Seize the day" was illustrated on the Grant of Arms made to Dr. Stephen Gregory Clackson under the hands and seals of Garter and Clarenceux Kings of Arms at Her Majesty's College of Arms on the 28th April 1998, and it was legally recognized as his motto in Scotland when the arms were matriculated in the Public Register of All Arms and Bearings (57th page of 74th volume) on the 23rd October 2001.