The amount in words
"One thousand two hundred and fifty euros and thirty cents." It looks like a formality inherited from cheques, and in some countries it is still expected on invoices, contracts and customs paperwork. The reason it survives is practical: digits can be altered with a pen, and a mismatch between the figures and the words is immediately visible.
What it is actually for
A written amount is a checksum a human can verify. Adding a zero to a figure takes a moment; making the words agree with it takes rewriting the line. It also removes ambiguity about separators — 1.250 means one thousand two hundred and fifty in some countries and one and a quarter in others, and the words settle it. Where a document will be read by someone who does not share your number formatting conventions, the written line is worth having whether or not anyone insists on it.
How the line is built
The number is split into the major unit and the minor unit, each converted separately, and joined with the currency's own names: euros and cents, pounds and pence, Turkish lira and kuruş, rupees and paise. The unit names have to agree in number — one euro, two euros — which is why the app stores the singular and plural of both the major and the minor unit for each currency rather than gluing an "s" on the end. For a currency with no minor unit, such as the yen, there is no second half to write at all.
The details that get it wrong elsewhere
Three mistakes turn up constantly in generated documents. Using the wrong minor unit name — cents on a pound invoice instead of pence. Getting the plural wrong for currencies where it is irregular. And writing a decimal that does not exist, such as "zero cents" on a yen amount. The line has to be generated from the currency, not from a single hardcoded template, which is why it is worth checking on the first document you issue in a currency you have not used before.
When to include it
If your country expects it on invoices, include it — the requirement is national, and this is one of the places where practice differs sharply from one place to the next. Beyond that, include it whenever the document travels: export paperwork, anything going through a bank or a customs process, high-value contracts, and any invoice sent somewhere that formats numbers differently from you. On a routine domestic invoice for a modest amount it is optional, and most people leave it off.
Frequently asked questions
Is writing the amount in words required?
It depends on your country and on the type of document. It is common in contracts and export paperwork and expected on invoices in some jurisdictions. Check what applies to you.
What language should the words be in?
The language of the document. The app keeps the document language separate from the interface language, so you can work in one and issue in another.
How are cents written?
As the currency's own minor unit, with the correct plural — pence for pounds, cents for euros and dollars, kuruş for Turkish lira, paise for rupees.
What about currencies with no cents?
There is no minor part to write. A yen amount is written as whole yen with nothing after it.
What if the words and the figures disagree?
Fix the document. A mismatch is exactly what the written line exists to reveal, and in some legal contexts the written amount is the one that prevails.
Do I need it on every invoice?
No. It earns its place on documents that cross a border, pass through a bank, or carry an amount large enough that an alteration would be worth someone's while.
Invoices where the totals actually add up. Invoice Maker builds invoices, proformas, quotes and receipts in your browser, does the money in whole cents so the VAT line never drifts, and exports a PDF. Nothing is uploaded.
Make an invoice in the browser