How to Create a Professional Invoice (Free, With Tax Done Right)

The short version

A professional invoice is not a design problem. It is a compliance and arithmetic problem with a design problem bolted on. Get the number, the date, the tax breakdown and the total right, and almost any clean layout will do.

Everything below is what you actually need, why each field exists, and how to produce it without a subscription. The tool referenced throughout — free invoice generator — runs entirely in your browser, so your client's billing details never touch a server.

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What makes an invoice legally valid

Most requirements you will see quoted are the union of the EU VAT Directive, UK VAT rules, and common GST/sales-tax regimes. In practice, a valid invoice carries these:

The four that get invoices rejected

If an invoice is going to be refused, it is almost always one of these:

1. A reused or duplicated invoice number.
2. Tax charged but no registration number printed — and therefore no valid input claim for the buyer.
3. A single tax total when more than one rate was applied, so the return cannot be filed.
4. A vague description, which turns a legitimate supply into an unverifiable one.

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How to number invoices so they survive an audit

The rules are short, strict, and entirely about consistency:

• Unique. Two invoices can never share a number.
• Sequential. Gaps are far more defensible than out-of-order numbering. If you cancel an invoice, void it visibly — do not delete it.
• Never reused. Not for a different client, not in a different year.
• Never reset mid-year. INV-2026-014 must never become INV-2026-001 again.

Which scheme to pick

A bare counter (1, 2, 3) is legal but tells you nothing at a glance. The most common professional choice is prefix + year + zero-padded sequence:

INV-2026-001
INV-2026-002
INV-2026-003

It is human-readable, sorts correctly in a spreadsheet, and makes an obvious gap visible. The invoice generator has a Next button that walks exactly this pattern and stores the counter in your browser, so next month continues where you left off.

One caution: the sequence lives in that browser. Clear your site data and it resets, and it will not follow you to another device. Keep your own record of issued numbers if invoices matter to you.

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Which tax rate to charge

The headline rate in your country is only the starting point, and the label matters as much as the number.

Three nuances that cause real errors:

The label is part of the compliance. An Ontario invoice quoting "GST 5%" when the correct rate is "HST 13%" is wrong on two counts. Most provinces replaced the federal GST with a single harmonised HST, and getting the label wrong signals to the recipient's accountant that you do not know your own regime.

Mixed rates are normal, not an edge case. A design studio charging 20% VAT on creative work but zero-rating a stock photography licence needs two rates in one document. A single global tax field cannot express this — which is why the generator lets you override the rate on any individual line item.

Discounts change the taxable base. If you give a genuine 5% loyalty discount, VAT is calculated on the discounted amount, not the original. On a £5,850 net that is £1,170 before discount and £1,111.50 after — not £1,170. Charging VAT on the pre-discount figure is one of the most common mistakes on UK invoices.

This table is a starting point, not tax advice. US sales tax depends on your exact state, county and city. Indian GST depends on the slab and whether the supply is inter-state. Brazilian ICMS changes per state. Several countries apply reduced rates to food, books, transport and energy. Confirm your own position.

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Invoice, quote or proforma — do not get this wrong

These three are routinely confused, and sending the wrong one is a reliable cause of delayed payment.

• Quote — states a price, and expires. Not a demand for money.
• Proforma invoice — a formal request for payment, typically used to collect a deposit before work begins. Not a tax document for a completed supply.
• Commercial (final) invoice — a demand for payment for goods or services already supplied. This one carries the full legal and tax weight.

Recording a deposit

If you have already taken a deposit, do not silently invoice the net figure. Show the invoice total, deduct the deposit, and state the balance:

Total due                    £7,258.00
Less deposit received       − £1,500.00
Balance due                  £5,758.00

That keeps the document self-explanatory and lets the buyer reconcile it against the deposit receipt without an email exchange. Builders, event agencies and anyone on a retainer will recognise the format immediately.

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A worked example

A UK brand studio billing a coffee roastery. Retainer and design work are standard-rated at 20% VAT; the stock photography licence is zero-rated.

Net subtotal                                    £6,470.00
Discount (5%)                                  − £323.50
VAT 20% (on £5,850.00 standard-rated)           £1,111.50
Total due                                       £7,258.00
Less deposit received                          − £1,500.00
Balance due                                     £5,758.00

Note that VAT is £1,170.00 × 0.95 = £1,111.50 — calculated on the discounted, standard-rated value only. The zero-rated licence contributes nothing to the VAT line, and the two rates are totalled separately.

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Choosing payment terms

Terms are not arbitrary. They follow the buyer's own payment cycle, and offering terms they can actually process is what turns a 30-day invoice into payment in 30 days instead of a queue.

A useful rule of thumb: you need roughly eight weeks of revenue in receivables to absorb one badly late payer. Moving from Net 30 to Net 60 doubles that exposure, so it should be a deliberate trade rather than a default.

When something does go late, escalate in stages: a short, factual note the day after it is due does no relationship damage; a formal demand around 14 days; a late-fee claim or formal recovery process at 30–45 days depending on the value and your local rules. Always quote the invoice number, the amount, and the date it fell due.

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How to actually make the invoice

You do not need invoicing software. You need a form, correct arithmetic, and a PDF.

The free invoice generator does this with no account, no watermark and no upload:

• 23 currencies, each formatted through the browser's own Intl API so the symbol lands on the correct side and separators match local convention.
• Per-line tax overrides, so mixed-rate and zero-rated invoices work in one document.
• 24 tax region presets that set the rate and the correct label.
• Discounts, shipping and deposits, with tax correctly assessed on the discounted base.
• Amount in words, which several jurisdictions require on a valid invoice.
• Real multi-page PDF download in A4 or Letter, with page breaks placed in whitespace so a split never cuts through a table row.
• Saved clients and business profile in your browser, so next month is a number bump rather than a re-type.

One limitation worth knowing

The exported PDF is a rendered image, so its text is not selectable or searchable. If your accountant needs an editable or importable file, use the browser's Print → Save as PDF, or transcribe the figures into your accounting software. Being clear about this up front is better than discovering it when a bookkeeper tries to extract figures.

Privacy

Everything runs client-side. Your rates, your client's tax ID and their billing address are never transmitted anywhere. That is a genuine advantage for sole traders and anyone under an NDA — but it also means the data lives only on that device, so download the PDF rather than assuming the page will still be there next week.

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A pre-send checklist

Run through this before every invoice leaves your outbox:

• Invoice number is unique, sequential, and not already used for a different client
• Issue date and due date are correct, and terms match what the client agreed
• Tax label and rate match your registration
• Any zero-rated or exempt line is genuinely exempt
• Discount applied before tax, not after
• Deposit and balance-due figures match payments actually received
• Buyer's PO number included, if they have one
• Logo is sharp at full size, and the totals table did not break across a page
• Payment details are correct and the account is open

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Frequently asked questions

What information must be on a legally valid invoice? A unique sequential number, issue date, seller details and tax registration number, buyer details, itemised descriptions with quantity and unit price, net total, tax broken out by rate, gross total in a named currency, and payment terms. Public-sector buyers also require their own PO number.

Do I have to register for VAT or GST to send an invoice? Registration thresholds differ by country and are separate from invoicing. If you are not registered you can generally still invoice, but you must not charge or claim the tax, and the wording should reflect that. Once registered, your registration number and a tax breakdown become mandatory.

Can one invoice contain different tax rates? Yes, and a genuine invoice often needs to. Each line must be described clearly and tax totalled separately per rate. A single global tax field is not sufficient for professional invoicing.

Is it acceptable to invoice in another currency? Yes, and stating the currency explicitly removes ambiguity in a dispute. You may still need to account for currency gains and losses, and cross-border supplies can trigger reverse-charge or import VAT on the buyer.

Should a discount reduce the amount invoiced? A genuine discount reduces the taxable value, so tax is calculated on the discounted amount. This is different from a promotional voucher or payment rebate. If unsure, confirm the treatment for your own jurisdiction.

How long should I wait before chasing an unpaid invoice? A brief factual reminder the day after it is due is appropriate and harmless. Escalate to a formal demand around 14 days, and to a late-fee claim or formal recovery at 30–45 days, depending on value and local rules.

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The bottom line

Number your invoices sequentially, print your registration number, break tax out by rate, calculate tax on the discounted base, and make it payable. The layout matters far less than those five things — and none of them require a subscription to get right.