You might be required to write a covering letter that will be added to your application once you have been contacted by a prospective employer or if you wish to approach the potential employer in writing. This document is of a more confidential nature than the CV or the résumé in the sense that you could communicate details of your existing remuneration package and when you would be available to fill the advertised position.
As the covering letter is your first written communication with the employer, it could create a lasting impression of your suitability for the position concerned. You must therefore pay special attention to accuracy, grammar, spelling, style and presentation. It is especially important to check the correct spelling of names, titles and contact details of the company you are dealing with.
The format of the letter will be a normal business letter and will start with a brief motivation of why you are applying for the position and what your present position entails. You could end the letter by providing your contact details should you be required to attend an interview.