How do I make an invoice?
- 1Add your business details and logo once — they are remembered for your next invoice.
- 2Fill in the client, the invoice number and dates, then add each item with its quantity, rate, discount and tax rate.
- 3Choose the currency, tax name (VAT, GST, sales tax), any discount, shipping and deposit, and pick a template and colour.
- 4Download the PDF, print it or save it as Word. “New invoice” saves this one and starts the next number.
How are invoice totals and tax worked out?
- 01Item amount = quantity × rate, rounded to the currency (cents, paisa)
- 02After discounts = item amounts − item discounts − discount on the whole invoice
- 03Tax added on top = amount at each rate × rate ÷ 100
- 04Tax inside prices = amount × rate ÷ (100 + rate)
- 05Total = after discounts + tax + shipping; balance due = total − amount paid
Each item is worked out as quantity × rate and rounded to the currency's smallest unit (two decimals for most currencies, none for the yen, three for the Kuwaiti dinar — the ISO 4217 minor units), with halves rounded up. Item discounts come off first, then the discount on the whole invoice, which is shared across the items in proportion so each tax rate is charged on the right amount. Tax is then worked out once for each rate on the discounted total of the items at that rate; tax authorities such as HMRC allow tax to be worked out per invoice like this or per line, so a line-by-line invoice can differ by a cent. Shipping is added after tax, and the amount already paid gives the balance due. All of this uses exact decimal arithmetic, so totals never drift by a cent.
When prices already include tax, the tax inside them is amount × rate ÷ (100 + rate): an item of 117 with 17 % tax holds 17 of tax. The PDF is written with real, selectable text using the PDF's built-in Helvetica font. That font only has Latin letters, so if a name or note uses another script (Urdu, Arabic, Hindi…) the PDF is made as a picture of the invoice instead, and signs like ₹ are written as the currency code.
Good to know
- Give every invoice its own number and never reuse one — tax offices expect a clear, unbroken series.
- Put a due date and full payment details (bank, IBAN, payment link) on the invoice so clients can pay at once.
- If you are registered for VAT, GST or sales tax, show your tax number (and the client's, where the law asks for it).
- Keep a copy of every invoice: tax offices usually ask businesses to keep records for several years.
Invoice generator — common questions
What should an invoice include?
At least: your name or business and contact details, the client's name and address, a unique invoice number, the invoice date, a description, quantity and price for each item, the total, and how and when to pay. If you charge VAT, GST or sales tax, most countries also require your tax number, the tax rate and the tax amount — check your tax office's rules (for example HMRC in the UK, the EU VAT Directive, or GST rule 46 in India).
What is the difference between an invoice and a proforma invoice?
A proforma invoice is a quote in invoice form, sent before the work or delivery so the buyer knows the exact cost (often for a deposit or customs). It is not a demand for payment and not a tax invoice. The real invoice is issued once the goods or services are supplied.
How do I work out the tax when my prices already include it?
Divide by 100 plus the rate and multiply by the rate: tax = price × rate ÷ (100 + rate). For 1,170 with 17 % tax inside, the tax is 1,170 × 17 ÷ 117 = 170, and the price without tax is 1,000. Choose “Prices include tax” and the generator does this for each rate.
How should I number my invoices?
Use a unique number that follows on from the last one, such as INV-0001, INV-0002 or 2026-001. A prefix or year is fine; what matters is that numbers aren't repeated or skipped. “New invoice” moves the number on by one for you.
Can I write the amount in words in lakh and crore?
Yes. Tick “Show the total in words” and choose Lakh, crore — for example Rupees One Lakh Twenty-Three Thousand Four Hundred Fifty-Six Only. Million and billion are used for other currencies.
Are my invoices and clients uploaded?
No. The invoice, the PDF and the Word file are all made in your browser, and your saved invoices, clients and logo stay in this browser's storage. Nothing is sent to us.
Sources
- GOV.UK — Invoices: what they must include
- HMRC — VAT guide (VAT Notice 700): calculating and rounding VAT on invoices
- European Commission — VAT invoicing rules (Council Directive 2006/112/EC, Article 226)
- CBIC India — CGST Rules 2017, rule 46: tax invoice
- ISO 4217 — Currency codes and minor units
Formulas last reviewed: September 30, 2026 ·How we check our formulas