An invoice is a sales document that a business sends to its customer. It lists the products and/or services that the business has provided and acts as an official request for payment for the provided goods or services.

In the UK, invoicing is mandatory for certain sales. This includes business-to-business transactions and transactions between VAT-registered businesses.

In the UK, invoices should include the following information:

• A unique invoice number

• Your company’s name, address and contact details

• Your customer’s name and address

• A description of the goods or services provided

• The date these goods or services were provided

• The invoice date

• The cost of the goods or services

• The VAT amount (if applicable)

• The total amount owed

A quote is a preliminary sales document provided to a customer as an offer before they accept the sale. It's essentially what customers use to "shop around" and find a good deal. It is non-binding and can either be accepted or rejected by the customer.

A proforma invoice is a document sent to a customer before all of the details of the sale have been finalised, but after the sale has been committed to. It will state ‘proforma invoice’ on the document to differentiate it from a full invoice, however, it will usually have the same format as a full invoice.

A full invoice is the completed document sent to a customer once the sale is final and payment is due.

Online invoice generators add up the totals for you, create a template for you, and ensure all the mandatory fields are input prior to saving. Therefore, you can always be certain that your invoice is complete, correct and compliant.

Excel, Word and Google Docs invoice templates often require manual entry, manual calculations and the entering of formulas. This can leave room for errors. However, if you prefer to use these tools, download our free invoice templates for Word and Excel.

You can also give our free online invoice generator a try or sign up to SumUp Invoices for free to access additional benefits.