The key to rejecting a job offer letter due to the offered salary is to be respectful and to keep the door open to the possibility of renegotiating the salary upward. If the job is acceptable and attractive in every way other than salary, there is a chance that further negotiations may bring the salary up to an acceptable level. If a job applicant would not accept the job even if the salary were raised, however, the rejection should be stated in a more firm and final manner.
Rejecting a job offer is a delicate matter. In most cases, the job applicant was interested in the job and wants to keep the lines of communication open with the hiring company in case future jobs open up. The key for an applicant in rejecting a job offer due to low salary is to make her value to the company clear. This opens the door to possible renegotiations. In fact, the applicant should express her willingness to negotiate the salary and to accept the job should her number be met. Adding research that shows the higher salaries of people in comparable positions in the same marketplace adds credence to the request for higher compensation. Throughout the entire process, including the rejection letter, the applicant should approach the person who wrote the original offer letter with respect and gratitude for their consideration.