How to write an invoice

Being paid on time is essential, and it all starts with an invoice.

Whether you use NabyPay to send invoices in seconds from your phone or invoice manually with one of our invoice templates, your invoices need to include the right information.

In our guide on how to write an invoice, we'll cover:

• What is an invoice?
• What's the purpose of an invoice?‍
• When should you send an invoice?
• Different types of invoices
• What an invoice must include
• Common invoice payment terms
• Accepting payments
• How to send an invoice
• What to do if a customer doesn't pay
• Tips to get paid faster

What is an invoice?

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

What’s the point 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.

When should you send an invoice?

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

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

Different types of invoices

There are two main types of invoice:

• Sales Invoice – most common, sent by you to the customer.‍
• VAT Invoice – use this type if you’re VAT registered.

What an invoice must include

What you must include on an invoice depends on whether you’re a sole trader or a limited company, and if you’re VAT registered (Gov).

NabyPay invoices are fully compliant and proven to help you get paid faster¹.

The asterisk (*) means optional but recommended.

For everyone

• Invoice number that is unique and sequential
• Date of the invoice and of the goods/services delivered
• Your business name, address and contact details
• Customer’s name and address
• Description of the goods/services (be clear and specific)
• The amount(s) being charged
• Total amount of invoice
• Payment terms (like when it’s due)
• How to pay (bank details, QR code, payment link)*

If you’re a sole trader

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

If you're a limited company

• Your full company name as registered at Companies House
• Company number*

If you're VAT registered

• VAT number
• Total VAT of invoice

Common invoice payment terms

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

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

Unless a payment date is included on the invoice, the customer must pay you within 30 days of receiving your invoice or the goods/services.

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

Accepting payments

There’s a few different ways to get paid, here are the most common:

1. Card payments

Most familiar to customers. In 2023 card payments accounted for 61% of all payments in the UK (UK Finance).

Accept card payments built-in to invoices with NabyPay.

2. Digital wallets

One-click pay-by-card using Google or Apple Pay.

Accept digital wallets  built-in to invoices with NabyPay.

3. Easy bank payments

The new way to pay by bank. No sort code or account number needed.

Accept easy bank payments built-in to invoices with NabyPay.

4. Bank transfer

The old-school, slow way to move funds between bank accounts.

Add bank details to invoices with NabyPay.

5. Cash

In 2023, cash accounted for just 12% of all payments in the UK (UK Finance).

Mark invoices as paid by cash with NabyPay.

Tip: Get paid faster by accepting familiar ways for customers to pay you, such as easy bank payments or card payments.

How to send an invoice

Most small businesses send invoices by email because it's easy, formal, and professional.

Before sending, make sure the invoice is:

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

With NabyPay, send invoices by email or with just a link.

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 usually works.
2. Follow up – Send a firmer, formal reminder with a clear deadline.
3. Charge interest or fees – legally, you can charge late payment interest on business debts (Gov).
4. Use a statutory demand - used to formally request payment yourself without a lawyer (Gov).
5. Consider legal options – if all else fails, debt recovery or small claims court are options.

Tips to get paid faster

• Use NabyPay - 92% of payments are made within one day¹
• Make it easy for customers to pay by bank or card
• Accept online payments for invoices
• Send the invoice promptly
• Set clear payment terms
• Follow up if it’s overdue