On the 28th of the month, the date you put on an invoice is the most consequential field on the form. It decides which month's profit the income lands in, and — more importantly — which VAT period it falls into.
Get it wrong by one day and you've moved money between two tax returns.
What the date actually controls
One date, three consequences:
- Which month's Profit & Loss shows the revenue.
- Which VAT return the output VAT belongs to.
- When the debt starts ageing — though that runs off the due date, not the invoice date.
An invoice dated 31 October belongs to October on all three counts. Dated 1 November, it belongs to November. Same work, same customer, same amount — different tax return.
Time of supply: what triggers the VAT
South African VAT doesn't key off the date you felt like writing on the invoice. Section 9 of the VAT Act sets the time of supply: generally the earlier of when an invoice is issued, or when payment is received.
"Earlier of" is the part to notice. If the customer paid you a deposit in October and you invoice in November, the VAT on that deposit was triggered in October — the payment came first. You cannot push it into the next period by dating the invoice later.
This is why deposits and advance payments trip people up at year-end. The money arriving is itself a trigger.
Most vendors account on the invoice basis: you declare the output VAT in the period the supply happened, whether or not the customer has paid. A limited set of smaller vendors may apply to use the payments basis instead. If you're on the invoice basis — and you probably are — an unpaid October invoice still puts October VAT on your October return.
Don't date an invoice into a period you've already filed
If you've filed your VAT201 for September and then raise an invoice dated in September, your books and your filed return no longer agree. The return said one number; the ledger now says another.
That's not fraud and it's not unfixable, but it is a discrepancy you now have to explain, and it will surface the next time anyone reconciles the VAT control account to the returns.
Your options, roughly in order of preference:
1. Date it in the current open period if the supply genuinely happened now. 2. Date it correctly in the closed period and correct the return, if the supply really did happen then. A VAT201 can be corrected; an unexplained gap is worse than a correction. 3. Never silently leave the two disagreeing and hope.
A system that warns you when you're posting into a filed period is doing you a favour, not nagging.
What a valid tax invoice must carry
Section 20 of the VAT Act sets out what a tax invoice must contain, and the date of issue is on the list — alongside the words "tax invoice", your name, address and VAT number, the customer's details, a serial number, a description of the goods or services, and the VAT either shown separately or stated as included.
Two things follow from that. First, the date isn't optional or cosmetic — it's a statutory field. Second, if you're not a registered VAT vendor you may not issue a tax invoice at all. You issue an invoice. Putting "tax invoice" on a document when you aren't registered, or showing VAT you aren't entitled to charge, is a real problem, not a formatting choice.
Back-dating versus forward-dating
Back-dating has a legitimate use: catching up. If you did the work in September and you're only capturing it now, dating it September is correct — that's when the supply happened. The invoice lands in September's figures where it belongs. The only caution is the filed-period problem above.
Forward-dating also has a legitimate use: billing in advance for something starting next month. But be clear about what it does — until that date arrives, the invoice is issued and posted, yet it isn't owed yet. It will be absent from your reports and your debtors until its own date comes round, then appear everywhere at once.
Neither is wrong. Both are wrong if you didn't mean to do them.
A month-end routine that prevents the mess
In the last three days of the month:
- Check the date on every invoice before you issue it. Most systems default to today, and most of the time that's right. It's the exceptions that cost you.
- Decide deliberately which side of the line each invoice falls. Work completed this month belongs to this month, even if you only get to the paperwork on the 2nd.
- Watch for deposits received. Payment received is itself a time-of-supply trigger.
- Don't date anything into a period you've already filed without deciding how you'll correct the return.
- Run your month-end checks before you file, not after. Draft invoices sitting unissued are income you've earned and not declared.
The short version
The date on an invoice is a tax decision, not a formality. One day's difference at month-end moves revenue between two VAT returns and two months' profit.
Pick it on purpose.