Tax invoice requirements: timing, receipt vouchers and bills of supply determine invoicing obligations and reverse charge invoicing. Suppliers must issue a tax invoice showing description, quantity, value and tax for goods at removal or delivery and for services within a prescribed period. Exempt or composition-scheme supplies require a bill of supply. Suppliers must issue receipt vouchers on advance payments and may issue refund vouchers if no supply occurs. Revised invoices may be issued within one month of registration for prior supplies. Recipients liable under reverse charge must issue invoices on receipt and payment vouchers when paying the supplier.