Delayed payment charges excluded from taxable value when separately billed; otherwise service tax applies to gross amount charged. Delayed payment charges imposed for late payments are penal in nature and do not form part of the consideration for taxable services, and thus are not includible in taxable value. However, service tax is chargeable on the gross amount charged, so if invoices or account statements do not show delayed payment charges separately, the tax must be applied to the entire gross amount; these charges are excluded from taxable value only when separately indicated in billing documentation.