Acting swiftly in declining a job offer ideally within 24 to 48 hours of receiving it is crucial. 1. Let your employer know as soon as possible.Avoid letting your employer wait too long. Focus on positive things to come up with a polite response to the job offer. You'll need to formally accept your offer. The easiest way is with gratitude. If the employer offered you a job, say, "Thank you for this offer. Learn how to write a job offer rejection letter that respectfully shares your choice without burning any bridges.