Cover letters and letters of interest, while similar, are two different things. In general, you use a cover letter when applying for one particular position that you already know is available, whether through a job listing or personal inquiry. A letter of interest, on the other hand, is most often used to express your interest in any openings a company may have available.
Letter of Interest
Write a letter of interest, also known as a letter of inquiry, when you have an interest in a particular company but may not know whether any positions are available. The letter’s purpose is to introduce your to the company and give a basic rundown of your qualifications and relevant experience. You can use the letter of interest to sell yourself to the company. It's usually beneficial to enclose your resume with these letters, so if the company is interested in you or has a position open up, it already has your resume on hand.
Send a cover letter with resume attached when you are responding to a job posting. The cover letter also introduces you to a company and summarizes the contents of your resume. The cover letter should list all of your strongest abilities in a clear, concise manner, and should never be longer than one page. Proofread your letter carefully. If your letter is rambling or has mistakes, potential employers may not even bother looking at your resume. Because cover letters are more focused on you, the candidate, rather than the position, they can often be a form letter you create ahead of time, allowing you to make only minor changes to adapt the letter to each specific position.
The biggest difference between a cover letter and a letter of interest is the knowledge you have when you use them. Because it is used when you are responding to a job listing, a cover letter should summarize your CV, emphasizing the points that make you the right person for the position. A letter of interest is more focused on why you are interested in the company and why you think you would be a good fit if any openings come up. You should customize these letters every time you send them out; customize a letter of interest to the company as a whole and customize a cover letter to a specific position.
Because of their similarities, cover letters and letters of interest are often terms that are used interchangeably, even by companies. In some cases you may need to use context clues in the ad or job posting to decide which one the employer actually wants. If you're responding to a job ad, you know a position is available; therefore, a letter of interest is not necessary. If you're on a company’s employment or HR page, however, a letter of interest is what you will need to send.
You can use a letter of interest as a cover letter in some situations; for example, a company may ask for a letter of interest, but you would like for HR to have your resume in case a position opens up. In this situation, you would not want to send a cover letter in addition to the letter of interest, so the letter of interest could serve as the cover letter. Both a cover letter and a letter of interest should strive to make you memorable and set you apart from other applicants
Whether you decide to use a cover letter or a letter of interest, be sure you follow any instructions given by the company. Most employers will state whether email is acceptable or if you should fax or mail the letters. If the employer prefers email, send it in the requested format, whether PDF or word processing document.