What to put on an invoice
An invoice is a request for payment that has to survive three readers: the person who approves it, the accountant who books it, and possibly an auditor years later. Every field on it exists because one of those three needs it. Below is what goes on the document and why — and where the requirements stop being universal and start being your country's business.
The four the app will not let you skip
Before it will call a document finished, the app checks four things: your name as the seller, the client's name, a document number, and at least one line with either a description or a price. These are not a legal minimum — they are the point below which the document stops being usable. An invoice without a number cannot be referenced in a payment, an invoice without a client cannot be matched to a purchase order, and an invoice with no lines is not asking for anything. Everything else is a warning at most, so that a draft is never blocked from taking shape.
Who, what, when, how much
The body divides into four blocks. **Who**: your business name, address and tax identifiers, then the same for the client — the buyer's details matter as much as yours, because the buyer's accountant needs to prove the expense is theirs. **What**: a description line per item, with quantity, unit price and, where you charge it, the tax rate. **When**: issue date, and separately the due date — these are different dates and conflating them is the most common cause of an invoice being paid late without anybody being at fault. **How much**: subtotal, discount if any, tax, total, and the currency stated explicitly rather than implied by a symbol.
The fields people forget
Payment details are the most commonly missing block: bank account, reference to quote, and what the client should write as the payment reference so you can match the money when it lands. A purchase order or reference number, when the client works with them, is often the difference between being paid in a fortnight and being paid in a quarter. And the language of the document: an invoice sent abroad is read by people who do not speak yours, which is why the app keeps the document's language separate from the interface language — you can work in your own language and issue the document in English.
Where the universal part ends
Everything above is practice, not law. What a compliant invoice must contain is set by your national tax authority, and it varies: some countries require specific tax registration numbers on the face of the document, some require sequential numbering with no gaps, some mandate particular wording when tax is not charged, several now require electronic submission rather than a PDF at all. If the invoice is for a business in another country the rules of both sides can matter. Take the list above as the shape of a good invoice and confirm the mandatory fields with your own tax authority or accountant.
| Field | What it is for | Skipping it means |
|---|---|---|
| Seller name and address | Identifies who is owed the money | The app treats the document as unfinished |
| Client name and address | Lets the buyer book the expense to themselves | The app treats the document as unfinished |
| Document number | The handle everyone refers to it by | The app treats the document as unfinished |
| At least one line | The thing being charged for | The app treats the document as unfinished |
| Issue date | When the claim was made | Ageing and tax periods cannot be worked out |
| Due date | When payment is expected | "Overdue" has no meaning; expect late payment |
| Tax identifiers | Required in many countries; ask yours | May make the invoice non-compliant locally |
| Tax rate and amount | Shows what part of the total is tax | The buyer cannot reclaim it |
| Currency | Removes the ambiguity of a bare symbol | "$" means four different currencies |
| Payment details and reference | How to pay and how you will recognise it | Money arrives you cannot match to an invoice |
Frequently asked questions
What must an invoice legally contain?
That depends entirely on your country, and it is the one question we will not answer for you. The document shape in this guide covers what invoices normally carry; the mandatory list comes from your national tax authority.
Do I need a tax number on the invoice?
In many countries yes, and in some the buyer cannot reclaim tax without it. Check with your tax authority — this is exactly the field that varies most.
Can I invoice as an individual rather than a company?
In many places yes, under conditions about how often and how much. It is a question for your tax authority, not for a layout tool.
How long should I keep copies?
Retention periods are set nationally and are usually measured in years. Keep the PDFs somewhere durable; the app does not store them for you.
Does the invoice have to be signed?
Usually not for a normal commercial invoice, though some clients and some countries expect a signature or stamp. It costs nothing to add one if the client asks.
Can I send a PDF or does it have to be electronic?
A PDF is standard practice in most places, but several countries now require structured electronic invoicing for some transactions. Check the current rule where you are.
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