How to Write a Professional Invoice — Complete Guide

What is a professional invoice?

An invoice is a formal request for payment. It documents the goods or services you've provided, the amount owed, and the terms under which payment is expected. A professional invoice is one that contains all required information, is presented clearly, and reflects the standard of work your client has come to expect from you.

The distinction between a professional invoice and an informal one matters for several reasons. Professionally formatted invoices with complete information are processed faster by accounts payable departments. They create no back-and-forth ("can you resend with your address?"). They give your client what they need to claim input tax credits. And they position you as someone who takes their business seriously.

For Canadian freelancers and small businesses, a properly formatted invoice is also a legal requirement once you're registered for GST/HST. The CRA specifies what information must appear on invoices at different dollar thresholds, and failing to comply can result in your client being unable to claim tax credits — which creates friction in your business relationships.

Required elements — the complete list

Every professional invoice should contain the following information. These apply whether you're invoicing for design work, consulting, photography, development, or any other service:

1. Your full business name — exactly as registered, or your trading name if you operate under one
2. Your contact information — email address, phone number, and mailing address (required for GST invoices)
3. Your GST/HST registration number — if registered, formatted as "123456789 RT 0001"; required on invoices over $30 to GST-registered clients
4. Your client's name — the business name or individual you're billing
5. Your client's address — required on full GST invoices ($150+)
6. A unique invoice number — sequential, never reused
7. Invoice date — the date the invoice was issued
8. Due date — when payment is expected
9. Description of services — clear enough that someone else could understand what was delivered
10. Quantity and rate — hours and hourly rate, or flat fee per deliverable
11. Subtotal — total before tax
12. Tax — GST/HST amount shown separately, with the rate applied
13. Total amount due — the final number your client needs to pay
14. Payment instructions — bank transfer details, e-transfer email, or a payment link

Fourteen elements. It sounds like a lot, but most invoicing software — including GetMeInvoice — handles the majority of this automatically once you've set up your profile. The only thing that changes invoice-to-invoice is the client, the line items, and the dates.

Invoice numbering best practices

Your invoice number is a unique identifier for each invoice you create. It serves several purposes: it makes it easy to reference a specific invoice in email correspondence ("re: INV-2024-089"), it helps your client's accounts payable process the payment correctly, and it keeps your own records organised.

The most important rule is simple: never reuse an invoice number and never issue two invoices with the same number. Duplicates create accounting headaches for your clients and can raise flags in audits. Sequential numbering — where each invoice number is one higher than the last — is the standard approach.

Common formats include: INV-001, INV-2024-089, 2024-089, or a client-specific format like MERIDIAN-24-001. Any consistent format works. Year-prefixed numbers (INV-2024-089) are useful because they make it immediately clear when an invoice was issued, which is helpful when reviewing records years later.

Gaps in your sequence are fine. If you void invoice 088 and the next one you send is 090, that's perfectly acceptable. What's not acceptable is having two active invoices both numbered 088.

Setting payment terms

Payment terms tell your client when you expect to be paid. The most common terms are Net 14 (payment due within 14 days of the invoice date) and Net 30 (payment within 30 days). Some freelancers use "Due on receipt," which technically means immediately, though in practice it means whenever the client gets around to it — which is usually slower, not faster.

Research consistently shows that shorter payment terms result in faster payment. Net 14 outperforms Net 30, and Net 7 outperforms Net 14. Clients tend to pay by whatever deadline you set, so setting a shorter deadline without negotiating a longer one is almost always worth doing.

For larger projects, consider split payment terms: 50% deposit upfront (before work begins) and 50% on completion. This protects you against non-payment and aligns your client's financial incentive with the delivery of your work. It's standard practice in many creative industries and most clients expect it.

Whatever terms you use, they should appear clearly on every invoice. "Payment due within 14 days" or "Due: December 15, 2024" — both work. The explicit due date is often clearer because the client doesn't have to calculate when Net 14 falls from the invoice date.

GST and tax requirements

If you're registered for GST/HST in Canada — which you must be once your annual revenue exceeds $30,000 — you're required to collect and remit GST or HST on your taxable services, and to show the tax clearly on your invoices.

The applicable rate depends on your client's province. In Ontario, it's 13% HST. In BC, it's 5% GST (provincial PST is separate). In Alberta, it's 5% GST with no provincial tax. In Nova Scotia, New Brunswick, Newfoundland, and PEI, it's 15% HST. The full guide to Canadian GST rates by province is in our GST Invoice Requirements article.

Your GST/HST registration number must appear on invoices over $30 issued to GST-registered businesses. For invoices over $150 — which is most of what freelancers send — it's a firm requirement along with your client's name and address. The number format is your 9-digit Business Number followed by "RT 0001": for example, GST/HST # 123456789 RT 0001.

Show the tax as a separate line item on every invoice. Don't embed it in the line item price. Your client needs to see the GST/HST amount to claim their input tax credit, and burying it defeats the purpose of issuing a tax invoice at all.

How to send your invoice

The method you use to send your invoice affects how quickly you get paid. Email with a PDF attachment remains the most universal method — almost every client can receive and process it, and it creates a paper trail. Send the PDF from your business email address, not a personal Gmail or Hotmail account, and include a brief cover message that references the invoice number and due date.

A payment link — a hosted invoice page where your client can pay by card — is increasingly the fastest option. When the client can pay by card immediately upon reading the email, there's no delay caused by setting up a bank transfer or cutting a cheque. The trade-off is a processing fee (typically 2.9% + 30¢ per transaction), which you can either absorb or add to the invoice as a convenience fee where local regulations permit.

Whatever method you use, send the invoice within 24 hours of completing the work. Delays in invoicing signal that payment isn't a priority to you — and your client's behaviour will often reflect that signal back. The moment the work is done is the moment the invoice should go out.

Common invoicing mistakes

The mistakes that cause late or missed payments are almost always avoidable. Here are the most common ones:

• Wrong email address. Sending to the wrong contact is more common than it sounds. Verify the billing contact before sending, especially for new clients.
• Missing or incorrect GST number. Your client's accounts payable team may flag or reject invoices without a valid GST number if they need it for tax purposes.
• No due date. "Payment due upon receipt" is not a due date. "Due December 15, 2024" is. Be explicit.
• Vague service descriptions. "Design work" is not a description. "Brand identity design — logo, colour palette, and typography system" is. Vague descriptions delay payment because someone has to ask what it refers to.
• No payment instructions. If your client doesn't know how to pay you, they won't. Include your bank details, e-transfer address, or a payment link on every invoice.
• Invoicing late. The longer you wait to invoice after completing work, the lower your invoice sits in the client's mental priority queue. Invoice immediately.
• Not following up. A polite reminder at 7 days past due recovers most late invoices. Silence recovers none of them.

The fastest way to invoice

The fastest path from completed work to received payment is: invoice immediately using software that handles the formatting, tax calculation, and delivery automatically, then let automated reminders follow up if payment doesn't arrive on time.

Manually creating invoices in Word or Pages, calculating GST yourself, and copying in your bank details every time adds 15–30 minutes to every invoice. For a freelancer sending 20 invoices a month, that's 5–10 hours a month on administrative work that could be eliminated entirely.

GetMeInvoice is built for exactly this. Set up your profile once — your name, address, GST number, services library, and payment instructions — and every subsequent invoice takes under two minutes to create and send. The GST rate is applied automatically based on your client's province. The invoice number increments. The due date calculates from your payment terms. The PDF is generated and emailed with one click.