Job seekers usually apply for many positions while job hunting. It's not uncommon for an applicant to receive multiple offers at differing salary levels. For most applicants, a higher compensation package is more appealing than a lower package barring unusual circumstances. Once you have made the decision to turn down a job offer, you must determine how to approach the topic in a respectful and professional manner. You should treat the company that you are turning down as a potential networking contact and make an effort to sustain a relationship with them. You may not be at your new position forever. It's important to remain on good terms and keep lines of communication open with companies that valued your experience and personality enough to extend you a job offer.
Call the company to let them know that you will not be accepting their offer immediately after making your decision. The company is actively working to fill a particular position in order to increase their company's performance and efficiency. Sitting on a job offer for an extended period of time is unfair and unprofessional. Simply contact the hiring manager or their secretary and briefly explain that you regret that you will not be able to accept the position, but that you greatly appreciated the opportunity to interview with them and learn about the position. Do not state that the reason that you are not accepting the position is because another company has offered you a better salary package. If you are pressed for an answer as to why you are turning down the job, simply explain that another company has offered you a "better opportunity."
Send a follow-up letter to the hiring manager. Mention the aspects of the position that you considered to be positive and be complementary towards the company. Explain that you hope to maintain a professional relationship with the company going forward. Again, state your regret for declining the position and state your reason for declining in vague terms such as "after careful consideration of my current career goals, I have decided to accept different position where my skills can be used to generate substantial growth and advancement for the company." Couching your reason for rejection in terms of your desire to "help" another company gives a more professional and altruistic impression than "money is the only thing that matters to me." Conclude your letter with a statement offering the company to contact you if you can be of further assistance. Additionally, if you know of a candidate who may be a good fit for the position, offer to provide their contact information or resume.
Make contact with the company periodically by sending professional cards or posting a positive comment on its website. Establishing an ongoing professional network connection will help you in the future if you decide to search for another position or to help a friend, family member or colleague secure a new job.