What is an Invoice? Elements, Types, & Purpose

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An invoice is more than just a document requesting payment. It is crucial to sales transactions and ensures clear communication between businesses and clients.

Here, we’ll demystify the elements, types, and overall purpose of invoices, giving you the knowledge you need to manage your financial transactions confidently. 

Key Takeaways

  • Invoices are requests for payment.
  • Invoices serve as legal documents, contracts between buyer and seller.
  • Invoices are also crucial for tax purposes and financial forecasting.
  • Multiple types of invoices exist, each with distinct purposes and use cases.

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What is an invoice & how it works?

what is an invoice

An invoice is a detailed document a seller sends to a buyer outlining the products or services provided, their quantities, and the agreed prices.

It is a formal request for payment, typically within a specified time frame. After a transaction is complete or at set periods during ongoing work (weekly, monthly, etc.), the seller issues an invoice to the buyer to initial the payment process.

Historically, the origins of invoicing can be traced back to ancient Mesopotamia, with the Cuneiform invoice in 2900 BC.

It’s believed Sumerian temple priests invented this documentation to help them keep track of agricultural produce and byproducts like bread and wine.

This earliest iteration of the invoice featured simple drawings of the items that needed to be entered into the records.

Later, it evolved to feature the list of items and the price and quantity of each.

Examples of Invoices

Below are a few invoice template examples to see what how an invoice is structured and what one looks like.

Microsoft Item Invoice Template
See a live example here
See a live example here

Functions of Invoices

Invoices serve the most obvious function of getting paid for products or services rendered, but also serve many other purposes.

  • Maintaining records: They help businesses keep track of sales and services rendered, critical for financial management and inventory control.
  • Payment tracking: Invoices allow sellers to monitor which payments are outstanding or completed.
  • Easy tax filing: Detailed invoicing makes tax preparation more manageable by providing clear records of income and taxable amounts.
  • Legal protection: In the event of a dispute, invoices serve as legal evidence of the terms and conditions both parties agreed to.
  • Business analytics: Analyzing invoicing patterns can offer insights into sales trends, client behavior, and financial forecasting.

Types of Invoices

Different scenarios call for different types of invoices.

Pro Forma invoice

A pro forma invoice is an estimate or quote before delivering goods or services, outlining the expected charges.

It is sent before the sale is confirmed and used when buyers can’t proceed with an official invoice because the final details have yet to be confirmed.

Pro forma Invoice

See live example of a pro forma invoice here

Commercial invoice

A commercial invoice is used for international trade. It details the value of goods for customs clearance and serves as a contract with proof of sale between the two parties.

Commercial Invoice

See live example of a commercial invoice here

Credit notes

Credit notes are issued to correct a previously sent invoice or to grant a refund.

credit note template

See live example of a credit note here

Timesheet invoice

A timesheet invoice reflects hours worked and the corresponding rates. Freelancers and consultants most commonly use these.

timesheet invoice template

See live example of a timesheet invoice template here

Recurring invoice

These are used for ongoing services and sent at regular intervals, determined by the agreement between buyer and seller. It can be monthly, quarterly, etc.

Recurring Invoice template

See live example of a recurring invoice template here

Elements of an Invoice

A well-crafted invoice should include the following elements:

  1. The word “INVOICE” needs to be prominently displayed.
  2. Invoice number: A unique identifier for tracking and record-keeping purposes.
  3. Date of service rendered: The date services were provided or products were delivered.
  4. Date of sending invoice: The date of the invoice itself.
  5. Contact and name of org/seller: Contact information and name of who sold the products or services.
  6. Name and contact of buyer: Contact information and name of who purchased the goods or services
  7. Terms and conditions: Payment deadline, late fees, and other conditions.
  8. A line detailing each product or service: Detailed description of what was provided
  9. Cost per unit and quantity of product: How much each unit of product or service costs and how many were purchased
  10. Tax rates: Applicable tax rates and totals
  11. Total amount owed with currency: The total amount owed for all goods and services on the invoice and the currency you’ll be paid in.
  12. A personalized note: A thank-you or courteous note to the buyer.

Invoicing Tips

To streamline your invoicing process and ensure timely payments:

  • Automate: Use invoicing software to efficiently create, send, and track invoices.
  • Be Timely: Issue invoice immediately after delivering goods or services, unless otherwise agreed, to keep cash flowing.
  • Be Clear and Detailed: Avoid ambiguity to prevent delays; clarity expedites payment.
  • Follow Up: Politely remind clients of outstanding invoices as due dates approach.


Invoices are more than just bills; they are a testament to your professionalism and an integral part of your financial management strategy.

By understanding and implementing effective invoicing practices, you can ensure smoother operations, better client relations, and a stronger bottom line for your business.


Is an invoice a receipt or bill?

An invoice is not a receipt but a detailed bill a seller sends to the buyer, listing the goods or services provided, their prices, and the total amount owed.

It is essentially a request for payment issued before the payment is made that outlines the terms of the sale and indicates what the buyer owes for the goods or services received.

Does an invoice mean you’ve been paid?

No, an invoice does not mean you’ve been paid. An invoice is a payment request.

Payment is typically made after the invoice is received, according to the agreed payment terms (for instance, within 30 days of the invoice date).

The issuance of an invoice signifies a payment is due, but it does not confirm that payment has been made.

What is the purpose of an invoice?

An invoice plays a pivotal role in the sales process, acting as a bridge between delivery of service or product and payment, while also serving important functions in accounting, legal protection, and business professionalism.


FreshBooks is accounting software built for business owners and their clients. Balancing your books, client relationships, and business isn't easy.

Try it free
We earn a commission if you make a purchase, at no additional cost to you.

Lucinda has spent the last 15 years working from home as a freelance writer and WordPress designer, and throughout her career, she has worked directly with several digital marketing agencies with clients in the SaaS space, ranging from e-commerce platforms to procurement software.