Most invoices carry more than one date, and the fact that they are usually all the same day hides how differently they behave when they are not. Each answers a separate question: when was this document created, when did the thing being billed actually happen, and when does the money have to arrive.
The consequences of confusing them are concrete. The wrong date can put revenue in the wrong tax period, start a payment clock earlier or later than you intended, or make an invoice look overdue when it is not.
The dates and what each one controls
Three dates appear on almost every invoice, and a fourth matters in tax terms without always being printed.
The **issue date** — often just labelled "invoice date" — is when the invoice was created and became a record. It is the anchor for numbering sequence and, in most cases, the point from which payment terms are counted.
The **supply date** is when the goods were delivered or the service performed. Where it differs from the issue date, VAT rules generally require it to be shown separately, because it often determines which tax period the transaction belongs to.
The **due date** is when payment must arrive. It is derived from the issue date plus the payment terms, and it is what the invoice should state explicitly as a date rather than leaving the reader to count.
The **tax point** is the date that decides which VAT or GST return the transaction falls into. It usually follows the supply date, but specific rules can move it — receiving a payment in advance, or issuing an invoice within a set window after supply, can each set it.
| Date | Answers | Primarily affects |
|---|---|---|
| Issue date | When was this invoice created? | Numbering sequence; start of payment terms |
| Supply date | When did the work or delivery happen? | Which tax period; evidence of performance |
| Due date | When must payment arrive? | Ageing, late fees, collections |
| Tax point | Which return does this belong in? | VAT/GST reporting period |
| Payment date | When did money actually arrive? | Cash-basis revenue; receipts; reconciliation |
Why the gap between issue and supply matters
When you invoice on the day you finish the work, everything collapses to one date and none of this is visible. The distinctions appear when the invoice lags the work — a project completed on 28 March but invoiced on 4 April, or a month of services billed in arrears.
The year-end version of this is where real money moves. Work delivered in December and invoiced in January sits in different periods depending on which date governs. On accrual accounting the revenue generally belongs to the period of supply, not the period of invoicing, which is precisely why the supply date has to be recorded rather than assumed.
This is also why invoicing promptly is more than a cash-flow habit. A long gap between supply and issue creates ambiguity about which period the transaction belongs to, and ambiguity is what audits examine.
Counting to the due date
Payment terms are almost always counted in calendar days from the issue date. "Net 30" on an invoice issued 1 March is due 31 March — weekends and holidays included, because the convention is calendar days rather than business days unless the invoice says otherwise.
Two variants move the starting point rather than the count. End-of-month terms start the clock at the end of the month of issue, so "Net 30 EOM" on a 3 March invoice is due 30 April rather than 2 April. Month-following-invoice terms fix a day in the next month instead, so "15 MFI" means the 15th of the following month.
Because these conventions are not universally understood, the reliable fix is to print the actual due date. "Net 30" plus "Due 31 March 2026" removes every counting argument, including the surprisingly common one about whether day one is the invoice date or the day after.
Backdating, and why it is a bad idea
The temptation to date an invoice earlier than it was created is usually innocent — pulling revenue into a closing period, or making a late invoice look prompt. It is still a poor idea, and in some circumstances worse than that.
Practically, it breaks numbering. If invoice 240 is dated before invoice 239, your sequence no longer runs in date order, which is exactly the pattern an auditor looks for. Substantively, dating an invoice into a period in which the supply did not occur misstates which return it belongs in.
The legitimate tool for the underlying problem already exists: record the supply date accurately and issue the invoice with today’s date. That puts the transaction in the correct period on its merits, without a document that disagrees with reality about when it was written.
Common Mistakes
Printing terms without a due date
"Net 30" leaves counting to the reader, and readers count differently. State the calculated date on the invoice so there is nothing to interpret.
Omitting the supply date when it differs
Where the work happened in a different period from the invoice, both dates are needed — and in VAT jurisdictions the supply date is generally required content, not an optional extra.
Counting terms in business days
The convention is calendar days. Assuming otherwise makes you think an invoice is not yet due when the client thinks it is, or the reverse.
Backdating to move revenue between periods
It breaks numbering order and misstates the period. Record the supply date correctly instead and let the invoice carry the date it was actually issued.
Frequently Asked Questions
Is the invoice date the same as the date I send it?
Usually, and ideally yes. If you create an invoice on Friday and email it on Monday, the terms are still counted from the date on the document — which is one reason to issue and send in the same action rather than letting drafts age.
Which date do payment terms count from?
The issue date, unless the invoice specifies otherwise. EOM and MFI terms shift the starting point to the end of the month or a fixed day in the following month, which is why they should be spelled out rather than abbreviated alone.
What if the supply date and invoice date fall in different tax periods?
The tax point decides which return the transaction belongs to, and it usually follows the supply rather than the invoice. Record both dates and let your accounting treatment follow the tax point rather than the convenient date.
Can I change the date on an invoice I already sent?
No. Once issued, the invoice is a record. If the date was genuinely wrong, cancel it with a credit note and issue a corrected replacement, so the change is visible rather than silent.
Sources & Further Reading
- VAT guide (Notice 700) — time of supply and invoicing — HM Revenue & Customs
- VAT Directive 2006/112/EC — chargeable event and invoice content — EUR-Lex, European Union
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