Time of supply of services: earliest qualifying event fixes tax liability, with special reverse charge and voucher rules. Tax liability on services arises at the earliest applicable event: invoice issuance within the prescribed period or receipt of payment, provision of service or receipt of payment where invoice timing differs, or the recipient's book entry if neither applies. For reverse charge supplies the earlier of recipient's payment entry or a specified lapse after invoice governs, with recipient's books as fallback; nonresident associated enterprise supplies follow recipient's books or payment date. Voucher supplies are timed on issue if identifiable or on redemption. If none apply, the return due date or tax payment date fixes time of supply. Additions for interest, late fee or penalty are timed on receipt by the supplier.