An employee has the right to appeal against a decision made after a disciplinary hearing.
You should tell them about this when you give them written notice of your decision, and should give them a deadline to tell you they want to appeal.
Your employee's statement of terms and conditions of employment must legally include the person they can apply to if they want to appeal a disciplinary decision. It must also explain how to do this.
If the employee does decide to appeal, you should try to hold the appeal hearing as soon as possible.