A list of template letters for occasions on which one ought to apologize in writing, from Great Personal Letters for Busy People: 501 Ready-to-Use Letters for Every Occasion by Dianna Booher, published by McGraw-Hill in 2005. For not having written For forgetting someone’s name For failing to invite friend to party For making embarrassing remark For behaving inappropriately For a friend behaving inappropriately For missing anniversary For missing birthday For missing funeral For missing deadline For bouncing cheque to friend or relative