Service tax invoicing: continuous supplies must prompt invoices upon completion of contractual payment events; exchange fee tiers added. Amendment effective 1 April 2011: rule 4A replaces 'provision of' with completion of and mandates that for continuous services providers must issue invoices within fourteen days after each contract event obliging payment. Rule 6 clarifies treatment where invoice amounts are renegotiated for deficient services or contractual terms, requires refunds where applicable, and revises sub rule 7B to a tiered currency exchange fee structure with an annual, irrevocable option for the service provider.