Common medical billing mistakes include incorrect coding, missing or incomplete documentation, claim denials, delayed or incomplete payments, human error, and compliance issues. To avoid these mistakes, healthcare providers should stay updated with coding guidelines, ensure accurate documentation, review claims carefully before submission, follow up on outstanding claims promptly, use automated systems, train staff on data entry accuracy, conduct regular audits, and stay informed about regulatory changes. By addressing these common errors, healthcare providers can improve their billing accuracy, reduce claim denials, and enhance their overall financial performance.