If you've ever wondered whether "estimate," "quote," and "invoice" are interchangeable words, you're not alone. Plenty of small-business owners use them loosely — until a payment gets disputed or a customer says "I never agreed to that price." This is the difference, in plain English.

An estimate is a proposal. An invoice is a bill.

That's the one-sentence version. An estimate says "here's what I think this work will cost." An invoice says "here's what I'm charging you, please pay." Estimates are about the future. Invoices are about the past.

What's on each one

Estimate

Your business name and contact info
Customer name and job address
Estimate number and date prepared
An expiry date (e.g., "Valid for 30 days")
Itemized scope of work with quantities and prices
Subtotal, applicable taxes, and total
Exclusions and assumptions
Payment terms (deposit, progress, final)
Signature/acceptance line

Invoice

Your business name and contact info
Customer name and billing address
Invoice number and issue date
A due date (e.g., "Due in 14 days" or "Due May 30")
Itemized list of work actually completed (or goods delivered)
Subtotal, applicable taxes, and total
Your GST/HST number if registered
Accepted payment methods and instructions
Reference to the original estimate (if applicable)

Notice the small but critical differences. An estimate has an expiry date. An invoice has a due date. An estimate lists planned work. An invoice lists delivered work. An estimate asks for a signature. An invoice asks for payment.

What about a "quote"?

In Canadian usage, "quote" and "estimate" are mostly the same thing, but with a small distinction:

An estimate is an educated guess at price, usually with some wiggle room.
A quote (or "fixed quote") is a binding price you're committing to.

If you write "fixed quote" on the document, you're saying "this is the price, and I'll absorb the difference if my costs go up." If you write "estimate," you have a bit more legal room to revise — though you should always communicate changes in writing before doing extra work.

The legal weight: signed vs unsigned

An unsigned estimate is just a proposal. The customer hasn't agreed to anything. You can revise it, withdraw it, or let it expire — and so can they.

A signed estimate becomes the basis of a contract. The customer has accepted your scope and price; you've committed to deliver it. If the customer later says "I never agreed to $14,500," you point to their signature.

An invoice is a demand for payment. Once issued, it's a debt the customer owes you (subject to your stated payment terms). In Canada, an unpaid invoice generally accrues whatever late fees you stated on the invoice itself, and after the due date you can take collection action.

The pattern that protects you: signed estimate first, then invoice for work actually completed. Never invoice for something the customer didn't authorize in writing.

How Canadian sales tax differs between the two

Both estimates and invoices should show sales tax — but for slightly different reasons.

On an estimate: tax is shown so the customer knows the all-in price they'll actually pay. It's a courtesy and a transparency signal — not a legal requirement at the estimate stage.
On an invoice: if you're GST/HST-registered, you must show your registration number, the tax amount, and the total clearly. This is what allows your business customer to claim an input tax credit. The CRA has specific requirements that depend on the invoice total.

We cover all the Canadian tax details in our full guide to sales tax on invoices.

The estimate → invoice workflow

A clean job goes like this:

Send estimate. Itemized, with expiry date and signature line.
Customer signs. Now you have an authorized scope and price.
Collect deposit. Issue a deposit invoice for, say, 25% of the total.
Do the work. Keep notes if anything changes.
Change orders in writing. If scope changes, document and get a signature before doing extra work.
Send final invoice. For the balance owing, referencing the original estimate number.
Get paid. Follow up at 14, 30, and 45 days if needed.

Common mistakes that blur the line

Sending an "invoice" before work is done. If you need money upfront, send a deposit invoice — label it clearly. A regular invoice for unfinished work creates a legal mess.
Numbering estimates and invoices in the same sequence. Keep them separate. Estimate #2026-0142 and Invoice #2026-0142 referring to different things will confuse everyone, including you, in two months when you can't remember which was which.
Treating verbal acceptance as agreement. "They said okay over the phone" is not a contract. Get the signature on the estimate before starting work.
Not stating an estimate expiry. Without one, a customer can hold you to old prices forever.

Convert estimate to invoice in one click

Once an estimate is accepted, the cleanest workflow is to convert it directly into an invoice — same line items, same customer, same taxes, just a new document number, a due date, and "Invoice" at the top instead of "Estimate."

That's exactly what Electrified Estimates & Invoices does: build the estimate, send the PDF, get approval, and convert to an invoice in one click. $5/month CAD plus applicable taxes — get started.