Section 12 - Time of supply of goods.

Tax liability arises at time of supply: earlier of invoice date or payment; special rules for reverse-charge and defaults

Liability to pay tax on goods arises at the time of supply, which is generally the earlier of the invoice issuance (or last permissible invoice date) and the receipt of payment; modest inadvertent excess payments may be treated as invoiced at the supplier's option. For reverse-charge supplies the time of supply is the earliest of receipt of goods, payment date as recorded or debited, or the day after thirty days from invoice issuance, failing which the entry in the recipient's books governs. If none of these apply, the time is the tax-return due date or, otherwise, the date of tax payment. Interest or penalties accrue when received.