The core difference

A quotation is an estimate you send before work begins — it proposes a price for the client to review and approve. An invoice is a request for payment sent after (or during) the work, based on what was actually agreed or delivered. A quotation is a proposal; an invoice is a demand for payment.

Why mixing them up causes real problems

Sending a document labeled "Invoice" when you actually mean "here's my estimate" can create the impression that payment is due immediately, which damages trust with a new client. Conversely, sending a "Quotation" after work is already complete makes it look like you haven't formally billed them at all, which can delay payment because it doesn't read as an official request.

What a good quotation includes

  • An estimated cost breakdown by item or service, similar to an invoice's line items
  • A validity period — "This quote is valid for 30 days" — since prices for materials or time can change
  • Clear terms about what happens if scope changes after acceptance
  • A space for the client to formally approve or sign off, converting it into an agreement

The typical workflow

  1. Quotation sent — you propose the price and scope.
  2. Client approves — verbally, by signature, or by email confirmation.
  3. Work is completed (or delivery milestones are reached).
  4. Invoice sent — based on the approved quotation, now formally requesting payment.

Keeping the quotation number referenced on the final invoice ("Ref: Quotation #Q-2026-014") makes it easy for both sides to trace the final bill back to what was originally agreed — useful if scope or pricing shifted slightly along the way.

When you might skip the quotation step

For small, fixed-price, repeat work with an existing client, sending a quotation every time can feel unnecessary. In that case, agreeing on pricing once (even informally) and moving straight to invoicing for each job is common practice — just make sure the agreed rate is documented somewhere both sides can refer back to.

Creating both from one consistent format

sedoc's Quotation Maker uses the same clean, branded layout as the Invoice Generator, so clients see a consistent look from your first estimate through to final payment — and converting an accepted quote into an invoice takes seconds.