Time of supply of services: tax arises at the earliest of invoice issue, payment receipt, service provision, or recipient accounting. Time of supply for services is the earliest of invoice issue within prescribed time, receipt of payment, provision of service when invoice deadlines are missed, or the date the recipient records the service; for reverse charge supplies the earlier of recipient payment, the date following sixty days from supplier invoice or recipient-issued invoice applies, with recipient book-entry as a fallback; if indeterminate, return filing date or tax payment date governs, and additions like interest or late fees are taxable when received.