Sick leave letter is relatively similar to an urgent leave letter because the cause of your absence is not preplanned. Though the format of letter writing does not change, still you are not sure how many days you will take off. If the sickness is minor then it is easy for you to mention the days you intend to take off, or according to the doctor’s advice you can mention the resting days. Make sure you send your leave letter as soon as possible.
The address in your letter is basically the initial portion of your letter. You are about to write a formal letter so make sure that the selection of words while addressing are formal and professional. Always use the proper professional terminology that is considered to be acceptable in your office. Also, make sure that you follow the proper format that is used for your company's internal communications.
The second thing is the body of the letter in which the request, reason and the date of your leave is mentioned. Make sure that you have all the fact and figures correct and accurate. You do not want to put in the wrong dates or names as this can be rather unprofessional and could get you in trouble later down the line. Make sure your sentence and paragraph structure follow a smooth flow and is readable. You want the reader to understand the message that you are trying to convey at a quick glance. The reader should not have to go over the letter more than once to get the meaning.
Be specific and clear about the reasoning as well as the dates on which you will not be able to perform your duties. Make sure that you give a proper reasoning and not just some lame excuse which seems trivial or unimportant.
The dates should be stated in bold letters to avoid confusion and ambiguity. Make sure the dates are correct so that there is no ambiguity in the days that you will be out of the office.
In the end mention the addresses correctly and make sure that you have stated your contact information as well, because you boss might need to ask you any sort of important information related to the office. It is always a good idea to give a contact phone number or email address in case their is an issue at the office that might need your attention or assistance.