In some cases, it means a great deal how you word your proposal to a client. Calling your proposal an estimate, job quote or statement of work (SOW) can mean different things to the client, and to the law. 

• As estimate is a "guestimate" or an approximation. Estimates are flexible and in most cases, negotiable.
• A quote provides your client with an exact price for the job or project. Quotes are exact, and in some cases, more legally binding than an estimate.
• A Statement of Work seeks to define liabilities, responsibilities and work agreements between two parties. It allows you to manage expectations and add a layer of detail about what the project will and will not cover.

Freshbooks - Quote vs Estimate 

Your Traderbase - Estimate vs Quote

Bradley Gross does a much better job of explaining these than I do. Check out two of his podcasts on this topic.

Technology Bradcast 41 - Quotes: How Long? How Detailed? How Terrifying!

Technology Bradcast 21 - Quote vs Proposal vs SOW: A Primer

Law Office of Bradley Gross – Business Technology Law

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