The question relates to the difference between a Show-cause Notice and a Charge sheet. A Charge sheet is also technically a show-cause notice only. A show cause notice is a broader concept and a Charge sheet is a technical terminology largely derived from the Standing Orders. Both can be used unless an employee who is alleged to have committed misconduct is covered under the Standing Orders of the company, where there is a reference to a Charge sheet as a tool of the disciplinary process. In all other cases, a show-cause notice and a charge sheet differ only in name, but not in substance or force.
You can issue a show cause notice, and if the explanation tendered by the employee is not satisfactory, they can be proceeded against through a domestic enquiry. The gravity of the offense does not matter. But in essence, even in the show cause notice, the charges (or allegations) must be very specific and not vague or open for interpretation. Normally in a charge sheet, the clauses of the Standing orders under which the alleged misconduct is mentioned are also clearly stated so that there is no scope for interpretation.
In the absence of the standing orders applicable to that individual, you can use a Show-cause notice, and there is absolutely nothing wrong. A show-cause notice or Charge sheet should not contain any statement that precludes that the offense has been committed. It must only state that "it has been alleged that..." or "it has been reported that you have..." The show cause notice or charge sheet concludes with "Show cause, in writing within 3 days, as to why disciplinary action should not be taken against you. If your explanation is not received within the stipulated time, it will be presumed that you do not have any reasonable explanation to offer, and you will be proceeded against."
So confidently use either of the terminologies, as per the distinction I have suggested above.