This letter format is used for asking to leave office early. We have explained the reason in simple way as party at home. We need to mention the subject line for these kind of permission letters.
Subject: Half day leave
Requesting you to grant me to leave 2 hours earlier today(mention Date,Time) because I have to attend party at home, As important I cannot afford to miss.
I will be finish my work early without any pending and stay an extra hour when it’s needed.
Thanks in advance