Changing your mind after verbally accepting is not ideal because the firm may already be planning around your decision, but it is still better to be clear now than to sign and reverse later.

If another offer is driving the decision, compare the options carefully and communicate quickly. The broader principles in this consulting job-offer negotiation guide can help you think through the decision before responding.

Once you decide, contact the recruiter directly, be concise, acknowledge the inconvenience, and avoid inventing a complicated justification. You may damage the relationship, but dragging the process out usually makes that worse.

Bad look, yes. Career-ending, no. Just tell them immediately.

Way better before signing/start date than backing out the week before you join.