How to write an invoice

What is an invoice?

An invoice is a document you send to a customer to request payment for goods or services you've provided. It outlines what’s been sold, the cost, and how to pay.

What’s the purpose of an invoice?

Invoices keep your payments clear and professional. They show your customer what they owe, what it’s for, when it’s due, and how to pay. You also need them for your own records and taxes.

Different types of invoices

There are a few different types, depending on how your business runs:

• Sales Invoice – the most common. Sent by you to a customer.
• Purchase Invoice – one you receive from someone else.
• VAT Invoice – if you’re VAT registered, this shows the VAT rate and amount.

What an invoice must include

The essentials vary slightly based on whether you’re a sole trader or a limited company, and if you’re VAT registered.

For everyone

• A unique invoice number
• Your business name and address
• Customer’s name and address
• The invoice date
• A clear description of what you're charging for
• The total amount
• Payment terms (like when it’s due)

If you’re a sole trader

• Your name and any business name you use
• An address where legal documents can be sent

If you're a limited company

• Your full company name as registered at Companies House
• Your registered address
• Your company number

If you're VAT registered

• Your VAT number
• The VAT rate
• A breakdown showing the VAT amount and the total excluding and including VAT

Common invoice payment terms

Payment terms set the expectations. Here are some typical ones:

• Due on receipt – pay immediately
• Net 7 / Net 14 / Net 30 – payment is due in 7, 14, or 30 days
• End of month – due by the end of the month

Tip: Be clear and consistent with your terms. It avoids confusion later.

How people usually pay

There’s more than one way to get paid. Offer familiar options:

• Bank transfer – fast and common
• Cash – for in-person jobs
• Card payment – use NabyPay to accept card payments easily
• Easy Bank Payment – NabyPay’s one-click bank transfer. No sorting codes or account numbers needed

When should you send it?

For most service-based businesses, send the invoice as soon as the job is done. For longer projects, you might invoice upfront, halfway, or in stages.

If you're selling goods, send the invoice once they’ve been delivered or shipped.

How to send an invoice

Most small businesses send invoices by email. Tools like NabyPay let you create and send professional invoices in seconds, from your phone or desktop.

Make sure it’s:

• In PDF or a secure format
• Clearly titled “Invoice”
• Easy to read

What to do if a customer doesn’t pay

Sometimes it happens. Here’s what to do:

1. Send a polite reminder – a quick nudge works wonders.
2. Follow up – still no payment? Send a firmer reminder with a clear deadline.
3. Charge interest or fees – legally, you can charge late payment interest on business debts.
4. Consider legal options – if all else fails, debt recovery or small claims court are options.

Tips to get paid on time

• Send it promptly‍
• Set clear payment terms
• Follow up quickly if it’s overdue
• Make it easy to pay (add a link or QR code to pay online)
• Send invoices with NabyPay and accept card and bank payments