At the point of sale the question never arises: the simplified invoice is issued at the moment of sale and handed over before the customer leaves. The question begins with business transactions: a contract delivered over weeks, an advance paid before supply, a subscription renewing monthly — when is the invoice due in each case?
The general rule
The timing anchor is the supply date — the day the goods are delivered or the service performed. The VAT implementing regulations set the deadline for issuing a tax invoice at no later than the fifteenth day of the month following the month of supply. Waiting until the end of that window is permitted, but operationally it is a bad habit: a delayed invoice delays its receivable with it, and the month's tail piles up in one batch.
Why the document carries two dates
A Phase 2 invoice has two independent fields: the issue date (when the document was created) and the supply date (when the transaction happened) — and validation requires a standard invoice to state its supply date. When January's invoice is issued on the fifth of February, the supply date keeps the transaction attributed to its correct tax period, so it never slips between two returns.
Advance payments
Receiving money before supply creates an invoicing obligation to the extent of the amount received: an invoice for the advance is issued when it is collected, and the remainder is invoiced when supply completes. Practically: define the advance as an explicit line in your system, and link the completion invoice to what was already invoiced so the customer is never charged the value twice.
Continuous supplies
Subscriptions, rents and maintenance contracts are continuous supplies with no single delivery day. Invoicing here is periodic: each period gets its invoice, its supply date reflects its period, and the issuing deadline runs per period on its own clock. The common mistake: one annual invoice "to save effort" where the contract called for monthly invoicing — loading one tax period with what belongs to twelve.
The practical summary
- Immediate sale: immediate invoice — that is the simplified case by nature.
- Deferred supply: invoice at supply, never later than the fifteenth of the following month.
- Money received in advance: invoice to its extent, when received.
- Continuous: an invoice per period, with a supply date reflecting it.
This is where automation earns its keep: in alFatora, subscription and instalment invoices are scheduled automatically, so no deadline slips and no month-end tail piles up — try it in the free sandbox.
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