A quote tells a potential client how much something will cost. An invoice tells a client how much they owe. One comes before the work, the other comes after.

What Is a Quote?

A quote (also called an estimate or proposal) is a document that outlines the expected cost of goods or services before any work begins. It typically includes:

  • Description of the proposed work or products
  • Itemized pricing
  • An expiration date (how long the quote is valid)
  • Terms and conditions

A quote is not a bill. The client is not obligated to pay until they accept the quote and the work is performed.

What Is an Invoice?

An invoice is a formal payment request sent after goods are delivered or services are rendered. Unlike a quote, an invoice creates a legal obligation to pay. It includes:

  • A unique invoice number
  • Exact amounts for completed work
  • Payment terms and due date
  • Tax amounts if applicable

How a Quote Becomes an Invoice

The typical workflow looks like this:

  1. Quote — you send a proposed price to the client
  2. Acceptance — the client agrees to the quote
  3. Work — you deliver the goods or services
  4. Invoice — you send a formal payment request based on the agreed quote

The invoice amount may differ from the quote if the scope of work changed. It is good practice to communicate any price changes before sending the final invoice.

Example

A web developer quotes a client for a new website:

Quote #Q-2026-045

  • Website design and development: $4,000
  • SEO setup: $500
  • Quoted Total: $4,500
  • Valid for 30 days

The client accepts. After completing the project, the developer sends:

Invoice #INV-2026-089

  • Website design and development: $4,000
  • SEO setup: $500
  • Additional blog page (approved change order): $300
  • Invoice Total: $4,800
  • Payment Terms: Net 30

Common Mistakes

  • Using a quote as an invoice. A quote does not request payment. Always send a proper invoice when the work is done.
  • Not setting a quote expiration. Material and labor costs change. Without an expiration date, a client could accept a year-old quote at outdated pricing.
  • Changing the price without notice. If the final invoice is higher than the quote, explain the difference. Surprise charges damage client relationships.
  • Skipping the quote entirely. For larger projects, a written quote protects both parties by establishing the scope and cost upfront.