What Is a Tax Invoice? When You Need One and What It Must Include

Tax Invoice vs Regular Invoice

In everyday business conversation, people use "invoice" and "tax invoice" interchangeably. Technically, there is a distinction that matters for tax compliance.

A regular invoice is any document requesting payment. It may or may not involve tax.

A tax invoice is a specific document that meets the legal requirements of your country's tax authority, allowing the recipient to claim input tax credits (GST/VAT credits) on their purchase.

If you're GST/VAT registered and your clients are GST/VAT registered businesses, you must issue tax invoices — not just regular invoices. Your clients cannot claim their input tax credits without a valid tax invoice.

When You Must Issue a Tax Invoice

You must issue a tax invoice when:

You are registered for GST or VAT

You are making a taxable supply (most standard business-to-business sales)

The amount is above the threshold for a simplified invoice in your jurisdiction

You do not issue a tax invoice when:

You are not registered for GST/VAT (below the registration threshold)

The supply is exempt or zero-rated (different rules may apply)

The supply is to a consumer who doesn't need input tax credits (some countries allow simplified receipts for B2C)

What a Tax Invoice Must Include (Australia GST)

Under Australian tax law, a valid tax invoice must include:

The words "Tax Invoice" clearly stated

Your business name and ABN

The date the invoice was issued

A brief description of the goods or services supplied

The GST amount charged (or a statement that the total includes GST)

The total price (including GST)

For invoices over A$1,000: the buyer's identity or ABN

If any of these elements are missing, the invoice is not a valid tax invoice under Australian law. Your client cannot claim GST credits on it.

What a VAT Invoice Must Include (UK)

Under UK law, a full VAT invoice must include:

A sequential invoice number

Your VAT registration number (format: GB XXX XXXX XX)

The invoice date

The tax point (date the supply was made, if different from invoice date)

Your name, address, and business details

Client's name and address

Description of the goods or services

The net amount for each item (excluding VAT)

The VAT rate applied to each item

The total VAT charged

The total amount including VAT

For invoices under £250, a simplified VAT invoice is allowed: your VAT number, the invoice date, description of goods/services, and the tax-inclusive total with the applicable rate noted.

The EU VAT Invoice Requirements

EU member states have broadly harmonised VAT invoice requirements under the EU VAT Directive:

Invoice number (sequential)

Issue date and supply date (if different)

Your VAT identification number

Buyer's VAT number (for B2B intra-EU supplies)

Both parties' names and addresses

Description, quantity, and unit price of goods/services

Net amount, VAT rate, and VAT amount

Total amount payable

Cross-border EU transactions have additional requirements (e.g. "reverse charge" notation where applicable).

What Happens If You Issue an Invalid Tax Invoice

If your invoices are missing required elements:

Your clients cannot claim input tax credits — which they will notice when their accountant reviews the invoices

You may be required to reissue corrected invoices

Tax authorities may disallow deductions based on non-compliant documentation

Systematic non-compliance can result in penalties

The good news is that getting it right is simple: invoicing software includes all required fields by default. Set up your ABN/VAT number in settings once, and every invoice automatically includes it.

Tax Invoice Settings in Quotation Expert

In Quotation Expert's business settings, enter your GST/VAT registration number and your applicable tax rate. Every invoice PDF then automatically includes your registration number, shows the tax amount as a separate line item, and labels the document "Tax Invoice" — meeting legal requirements without any manual effort.