Time of supply of goods determines tax liability: earlier of invoice issue or payment receipt, with reverse charge and voucher The time of supply determines tax liability and is generally the earlier of invoice issue (or last required invoice date) and receipt of payment; a nominal excess receipt may be treated as invoiced at the supplier's option. For reverse charge, timing is the earliest of receipt of goods, recipient's payment entry or bank debit, or the date after a prescribed period from invoice; if indeterminate, recipient's books govern. Voucher supplies are timed at issue if identifiable, otherwise at redemption. If none apply, timing follows the periodical return due date or the date tax is paid. Additions like interest or late fees are timed on receipt.