Quote vs estimate: what you're actually promising a client
The words aren't interchangeable, and the difference is money.
An estimate is a considered guess
An estimate is your best read of what a job will cost, offered up front and understood by both sides to be subject to change. It's useful for a client deciding whether to proceed. It is not a number you're committing to hold.
A quote is a commitment
A quote is a price you'll stand behind - a financial document and a promise. Once a client accepts it, it governs what you can bill. That's why a quote deserves more care than a copied-forward workbook: the number has to be right, and you have to be able to prove what it was.
Why the distinction costs margin
The danger is treating a quote like an estimate: sending a firm price built the same loose way as a guess. When the client queries it six weeks later, or scope shifts, a quote you can't reconstruct is a dispute you'll usually lose, and margin you'll usually give back.
How to make a quote you can defend
Price it from a catalogue so the build-up is consistent. Freeze it the moment you send, so the figures can't drift. Keep the acceptance on record (against the client's order number, with a timestamp) and note when the client first opened the link. A quote with that trail behind it ends most arguments before they start.
When scope changes: revise, don't rewrite
Scope grows. The right move is to revise, not to overwrite: a revision is a new numbered document, and the original stays on record. Extra work agreed on site goes on as an additive variation and is invoiced at the real total. Nothing you already committed to quietly disappears.