Check the below link for more formats http://www.aletterformat.com
Sub: Request for extension of leave – Reg.
Sir, I have applied and sanctioned 90 days leave with permission to leave the office during the month of October 2008 to appear the examination during the month of January 09. Now the university has post pond the examination schedule from 24-01-2009 to 30-01-2009. Hence it is requested that my leave period may please be extended further 30 days for appearing the examination.