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How to Number Your Invoices

2 min read2026/27 tax year

SARS requires every tax invoice, full or abridged, to carry a serial number and the date it was issued. The law doesn't prescribe a format, but a sensible numbering system saves you trouble at VAT return time and if SARS ever audits you.

What the number is for

The serial number lets you, your customer and SARS find one invoice among thousands. It also shows that your records are complete: if your invoices run 101, 102, 104, someone will ask what happened to 103.

Habits that work

  • Use one sequence, in order. INV-0001, INV-0002 and so on. Don't reuse a number, even for a cancelled invoice.
  • Don't delete a mistake; correct it. If an invoice is wrong after you've sent it, issue a credit note (for a reduction) or a debit note (for an increase) that refers to the original, rather than reusing or changing the number.
  • Keep a register. A simple list of number, date, customer, total and VAT makes your VAT return a matter of adding up.
  • Keep copies. SARS expects vendors to keep records, including tax invoices, for at least five years.
  • Separate sequences only for good reason. If you run two branches or two kinds of business, separate prefixes (A-0001, B-0001) are fine, as long as each sequence is complete.

Quotes and pro-formas

A quote or a pro-forma invoice isn't a tax invoice. Give them their own numbers (Q-0001, PF-0001) so they never break your invoice sequence, and don't put "tax invoice" on them.

Dates matter too

The date on a tax invoice is the date it was issued. Remember that a vendor must issue a tax invoice within 21 days of the supply.

Our invoice generator starts at INV-0001 and lets you set your own number for each invoice.

A simple register, worked through

Suppose you issue three invoices in March: INV-0041 for R11,500.00 (R1,500.00 VAT), INV-0042 for R2,300.00 (R300.00 VAT) and INV-0043 for R4,600.00 (R600.00 VAT). Your register shows output tax of R2,400.00 for the month, which goes straight onto your VAT return. If INV-0042 was wrong and you issued a credit note CN-0007 for R2,300.00, the register shows that too, and the month's output tax falls to R2,100.00. Nothing has been deleted, and anyone checking your books, including SARS, can follow every step from the invoice to the return.

Sources

This is general information, not tax, legal or financial advice.