A thank-you letter is a follow-up to an interview and can act as a secondary sales letter similar to your original cover letter. This is a very important document for your job search success. A thank-you letter is a professional and effective way to follow up and reiterate your desire for the position in consideration. Thank-you letters have the power to influence employment decisions. Your new thank-you letter will reinforce your candidacy, your skills, qualifications, and experience.