1. Buying back the same stock: If you try to use Credit for Sale (CFS) to buy back the same stock on the same day, it may be disallowed as it may result in peak margin shortfall, in case you do not have sufficient wallet balance.

  2. Margin shortfalls: If it's identified that you're using Credit for Sale (CFS) for new trades that lead to peak margin shortages, future CFS might be blocked to prevent penalties.