Guide · Invoicing
Tax invoice format and requirements: what every invoice needs
Where your business charges VAT, GST or sales tax, an invoice is a tax document, not just a bill. Here are the fields it usually carries, how the tax lines are built, and a worked invoice you can check yours against.
Updated · 6 min read
In short
A tax invoice usually shows both parties' names and addresses, your tax number, a unique sequential number, the date, each line's quantity, price and tax rate, the tax amount and the total. SimpleERP fills these from your country's profile on every invoice.
What must a tax invoice contain?
A tax invoice must let the buyer reclaim the tax they paid, where the system allows it, and let a tax officer trace the sale. The table lists the fields most systems ask for, with the values from one example: invoice INV-2026-0213 from Harbour Steel Furniture, the fictional business used across these guides, to Riverside Stores, with tax at 20%.
| Field | Example |
|---|---|
| A title that says what the document is | Tax Invoice |
| Supplier's name, address and tax number | Harbour Steel Furniture, 14 Quay Road, tax number 123456789 |
| Invoice number: unique and in sequence | INV-2026-0213 |
| Date of issue | 3 October 2026 |
| Buyer's name and address, and tax number where required | Riverside Stores, 8 Market Street |
| Description, quantity and unit | Steel rack 4 shelf, 2 each |
| Unit price and line value, before tax | $499.00 each, $998.00 |
| Tax rate on each line | 20% |
| Tax amount, by rate | $199.60 |
| Total payable | $1,197.60 |
The title differs by country. Australia and the United Arab Emirates use "Tax Invoice"; in the United Kingdom a VAT-registered business issues a VAT invoice; in the United States, where sales tax is not reclaimed by the buyer, an ordinary invoice is the norm. Check which your country expects.
Illustration of tax invoice INV-2026-0213 to Northside Retail with tax 10% and the amount in words.
How are the tax lines worked out?
Tax is worked out on each line at that line's rate, then added up by rate at the foot of the invoice. When an invoice mixes rates, the foot shows one row per rate, so the buyer and the tax officer can see what was charged at each.
| Line | Value before tax | Rate | Tax |
|---|---|---|---|
| Steel rack 4 shelf, 2 at $499 | $998.00 | 20% | $199.60 |
| Delivery to site | $60.00 | 20% | $12.00 |
| Assembly guide booklet | $5.00 | 0% | $0.00 |
| Totals | $1,063.00 | $211.60 |
Standard rates vary widely: 20% VAT in the United Kingdom, 5% VAT in the United Arab Emirates, 10% in Australia, and sales tax set by state and city in the United States. The arithmetic is the same at any rate.
What are the rules for invoice numbers?
Almost every tax system expects invoice numbers to be unique and to run in an unbroken sequence, so a missing number can be explained. Most allow more than one series, for example one per branch or per year, as long as each series is unbroken.
- Never reuse a number, even for a cancelled invoice. Cancel it and keep it in the sequence.
- Never edit an issued invoice to change the amount. Correct it with a credit note or a debit note.
- Start a new series on a clear date, such as the first day of the financial year, so the years never mix.
When must a tax invoice be issued?
Most systems set a deadline counted from the supply: the delivery of the goods or the completion of the service. The deadline differs by country, from a few days to a month. Issuing late rarely changes when the tax is due, so late invoices only open a gap between your books and your tax return.
What is the difference between a tax invoice, a credit note and a debit note?
A tax invoice records a taxable sale, a credit note reduces the value or tax of an earlier invoice, and a debit note increases it. Notes refer to the original invoice by number and date.
| Document | Issued when | Effect on tax |
|---|---|---|
| Tax invoice | A registered business makes a taxable sale | Output tax for the supplier; input tax for a registered buyer where it can be reclaimed |
| Credit note | Goods are returned, or the price or tax was too high | Reduces the supplier's output tax |
| Debit note | The price or tax was too low | Increases the supplier's output tax |
How does SimpleERP build a compliant tax invoice?
SimpleERP fills the fields from your setup, your country's profile and your customer record, so the person invoicing only picks the customer, the products and the quantities.
- Your business name, address and tax number, with the label your country uses, such as VAT number, TRN or ABN
- The invoice title your country uses, such as Tax Invoice or Invoice
- A tax rate on every line, from the product, with the tax totals shown by rate
- Numbering in one unbroken series per year, with a live preview in Settings
- Round off and the amount in words in your currency on the A4 print
- Sales register and a tax summary by rate for your accountant's return checks
See it on the billing software page. In India, a GST invoice has its own fields, such as the GSTIN, HSN code and place of supply: see the GST invoice format (India).
FAQ
Questions, answered
What is the difference between a tax invoice and a normal invoice?
A tax invoice carries the details a tax authority needs: your tax number, the tax rate and tax amount, and a unique sequential number. Where the buyer can reclaim tax, they usually need a valid tax invoice to do it. A normal invoice may simply ask for payment.
Do I need the buyer's tax number on the invoice?
It depends on the country and the sale. Many systems ask for it on business sales above a value, or when the buyer accounts for the tax under a reverse charge. Check your tax authority's guidance; SimpleERP prints it when the customer record holds one.
Can I edit a tax invoice after issuing it?
You correct an issued invoice with a credit note or debit note rather than editing it. In SimpleERP a posted invoice is frozen; you cancel it, which reverses its entries, or raise a note against it.
Is the amount in words required on an invoice?
Rarely by law, but buyers and banks in many countries expect it. SimpleERP prints the amount in words in your currency, for example dollars and cents or dirhams and fils, on every invoice.
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