What to include on an invoice
An invoice does two jobs at once. It asks a person to pay you, and it stands as a tax record for both sides for years afterwards. Those jobs pull in different directions — the first rewards brevity, the second rewards completeness — and most bad invoices are bad because they only did one of them.
The fields almost every jurisdiction expects
Requirements differ in detail, but a common core runs through nearly all of them. An invoice missing any of these is likely to be queried, delayed, or rejected by an accounts system before a human ever reads it.
| Field | Why it is there | Where people get it wrong |
|---|---|---|
| The word “Invoice” | Distinguishes it from a quote, estimate, or statement. | Sending a document headed “Statement” and expecting it to be paid. |
| Unique invoice number | Identifies the document in both parties' records; sequential numbering is a legal requirement in many places. | Restarting numbering each year without a scheme, or reusing a number after a cancellation. |
| Invoice date | Usually starts the payment clock and fixes the accounting period. | Dating it the day you got round to sending it rather than the day work completed. |
| Due date | Removes all ambiguity about when payment is expected. | Writing only “Net 30” and leaving the reader to compute a date. |
| Your legal name and address | Identifies the supplier for tax purposes; a trading name alone is often insufficient. | Using a brand name that does not match the entity receiving the money. |
| Client's legal name and address | Identifies who owes the debt — which matters enormously if you ever have to enforce it. | Addressing it to an individual contact rather than the company that is liable. |
| Description of what was supplied | Lets the client verify the charge and satisfies record-keeping rules. | A single line reading “Consulting” for a five-figure sum. |
| Quantity, rate and line total | Shows how the number was arrived at. | Rounding at the line level so the totals do not reconcile. |
| Subtotal, tax and total due | Separates the taxable base from the tax, which most tax regimes require. | Quoting one tax-inclusive figure with no breakdown. |
| Tax registration number | Required on tax invoices in VAT/GST countries once you are registered. | Omitting it, which can make the invoice unusable for the client's reclaim. |
| Payment details | Removes the last excuse for delay. | Bank details for an account whose name differs from the invoicing entity. |
| Currency | Unambiguous on cross-border work, where “$” is genuinely uncertain. | Relying on a symbol instead of a three-letter code. |
Fields that are optional but earn their space
- Purchase order or reference number. Where a client uses POs, an invoice without a valid one is frequently rejected automatically. Ask for it before you invoice, not after.
- The name of the person who commissioned the work. Accounts departments route unfamiliar invoices to whoever they think approved them. Telling them removes a delay.
- Period covered. For retainers and ongoing work, stating the dates prevents the “didn't we already pay this?” conversation.
- Payment terms in words. A one-line restatement of the agreed terms on the invoice itself, so nobody has to find the contract.
- Late payment policy. A brief note that overdue amounts may attract statutory interest. Rarely acted on, occasionally decisive.
Match the name on the invoice to the name on the bank account. Payment systems increasingly verify that the two agree, and a mismatch can silently block a transfer that both parties believe has been made.
Regional differences worth knowing
- VAT countries (UK, EU and many others). A compliant VAT invoice generally needs your VAT number, the tax point, the rate applied, and the tax shown separately. Where the reverse charge applies to a cross-border supply, the invoice usually has to say so explicitly and show the customer's VAT number.
- United States. No federal invoice format. Sales tax is state and often local, and whether services are taxable at all varies by state — which makes describing the supply accurately more important than it looks.
- Canada. GST/HST invoices have prescribed content that scales with the value of the sale, including your business number above certain thresholds.
- Australia. A valid tax invoice generally requires the words “Tax invoice”, your ABN, and the GST amount or a statement that the total includes GST.
If you invoice across borders, the safest habit is to include the full set of fields every time rather than tailoring per country. Nothing is lost by including a reference the recipient does not need.
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Describing the work so it survives scrutiny
The line-item description is the field people rush and the one that causes the most delay. It is read by someone who did not commission the work and has no idea what it was. Write for that reader.
- Name the deliverable, not the activity. “Brand guidelines document, 24 pages” beats “design work”.
- Include the period or date. Anchors the charge against the client's own records.
- Split anything separately negotiated. If a licence, a rush fee or expenses were agreed as distinct items, invoice them as distinct items.
- Keep expenses visible. Rebilled costs folded into a fee look like padding when they are queried.
Common questions
Does an invoice need a signature?
Almost never. Invoices are not contracts, and in most jurisdictions an unsigned invoice is entirely valid. Some clients ask for one as an internal control, which is a preference rather than a requirement.
Can I invoice without a registered business?
In most places a sole trader can invoice under their own name, showing their personal legal name and address. Tax registration becomes relevant once you pass local thresholds, at which point additional fields become mandatory.
What if I need to correct an invoice I already sent?
Do not edit and resend under the same number. Either issue a credit note cancelling the original and raise a fresh invoice, or issue a corrected invoice with a new number that references the one it replaces. Silently changing a sent document breaks the audit trail on both sides.
Should the invoice be a PDF?
Yes, in practice. A PDF renders identically everywhere, cannot be accidentally edited, and is what accounts systems expect to archive. A spreadsheet or a body-text email invites both alteration and misreading.
How detailed do line items need to be?
Detailed enough that someone who was not involved can match each line to something they recognise. That usually means one line per deliverable or per agreed rate, not one line per hour and not one line for everything.
General information, not legal or tax advice. Mandatory invoice content is set by national law and changes. Confirm what applies to you before relying on this as a compliance checklist.
Related guides
- Invoice numbering and record keepingSchemes that stay valid, and how long to keep them
- Sales tax and VAT on invoicesWhen to charge it and how to show it
- Invoice payment terms explainedNet 30, EOM, 2/10 and what they cost you
- How to chase an unpaid invoiceA five-stage escalation ladder