Time of supply of services establishes earliest event triggering GST liability: invoice, payment, provision, or voucher redemption. Time of supply of services is the earliest qualifying event fixing tax liability: where invoice is issued within the prescribed period, the earliest of invoice issue or receipt of payment; otherwise the earliest of provision of service or receipt of payment; or the recipient's book entry if those do not apply. Definitions cover deemed supply extent and the date of receipt of payment. Special rules govern reverse charge supplies (earlier of recipient payment entry or date after sixty days from supplier invoice, with fallback to recipient book entry and specific rule for associated enterprises abroad), vouchers (issue or redemption), periodical-return or payment fallbacks, and additions to value effective on receipt.