Unique identification number for transactions ensures each electronic ledger debit or credit is traceable through the common portal. A Unique Identification Number must be generated at the Common Portal for each debit or credit to the electronic cash or electronic credit ledger; the number for credits discharging liability must be recorded in the corresponding entry of the electronic tax liability register, and a Unique Identification Number must also be generated for credits to the electronic tax liability register arising for reasons other than discharge of liability.