Acting swiftly in declining a job offer ideally within 24 to 48 hours of receiving it is crucial. The easiest way is with gratitude.If the employer offered you a job, say, "Thank you for this offer. Focus on the matters that influenced your decision without mentioning why you accepted a different offer. 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. As long as you're honest, give them plenty of notice, then that door should be open to you in the future once you outgrow your current employer.