Consultant Invoice Template Canada — Retainer, Hourly & Project Billing

Whether you are a management consultant billing a Bay Street client for strategic advice, a marketing consultant on a monthly retainer, or an IT consultant invoicing for a completed system migration, your invoice must reflect the billing model you agreed on — and comply with CRA requirements for GST/HST.

This guide covers all three primary consulting billing structures, what to include in each invoice type, a realistic Ontario example with HST at 13%, and how to handle travel expenses and late payment protection.

The Three Consulting Billing Models

1. Hourly Billing

Hourly consulting invoices are straightforward but require clear documentation. Clients want to know exactly what hours were worked and on what. Best practice is to include a time log summary directly on the invoice or attach a detailed timesheet.

A time log summary on the invoice might look like:

Feb 10  Strategy kickoff meeting (2.0 hrs)
Feb 12  Stakeholder interviews (3.5 hrs)
Feb 14  Market analysis research (4.0 hrs)
Feb 17  Draft report preparation (5.0 hrs)
Feb 18  Revision and final delivery (1.5 hrs)
Total: 16.0 hours @ $200/hr = $3,200.00

2. Project-Based (Fixed-Fee) Billing

Fixed-fee consulting engagements are billed against deliverables rather than hours. Your invoice should describe each deliverable and its value. Milestone billing — where you invoice at 30%, 60%, and 100% completion — is common for longer engagements. See our dedicated project-based invoice template for a milestone billing example.

3. Monthly Retainer Billing

Retainer arrangements provide your client with a set number of consulting hours per month for a fixed monthly fee. The invoice is simple — one line for the retainer fee — but should clearly specify the billing period and hours included. See also our retainer invoice template for more detail on rollover hours and overage billing.

What to Include on a Consultant Invoice

Standard Fields

• Your business name, address, email, phone
• GST/HST registration number (mandatory once registered — format: 123456789 RT0001)
• Client's business name and billing address
• Unique invoice number (e.g., INV-2026-017)
• Invoice date
• Payment due date — corporate clients typically expect Net 30

Consulting-Specific Fields

• Purchase Order (PO) number — most corporate clients issue a PO for approved consulting spend. Always reference it on your invoice (e.g., "PO# 45892"). Invoices without a PO number are often delayed in AP departments.
• Billing period — specify the date range (e.g., "Services rendered: February 1–28, 2026")
• Time log summary — dates, tasks, and hours worked
• Expense reimbursements — itemised separately from your professional fees
• HST amount and registration number
• Payment instructions — bank account for EFT/wire, or Interac e-Transfer email

Example: Ontario Management Consultant Invoice (Hourly, HST 13%)

The following invoice is for a Toronto-based management consultant billing a corporate client for February consulting services.

How to Invoice for Travel and Expenses

Consulting engagements often involve reimbursable expenses. Follow these best practices:

• Separate expenses from professional fees on the invoice — list them as distinct line items
• Attach receipts — scan and email original receipts, or reference "receipts attached" on the invoice
• Mileage: CRA's 2026 prescribed rate for the first 5,000 km is $0.72/km for most provinces. Using this rate keeps reimbursements non-taxable for the client in many cases.
• HST on expenses: If you paid HST on a reimbursable expense (hotel, flights), you can include HST on that line item as well — just be consistent with your approach and discuss it with your client upfront.
• Expense cap: Some consulting agreements have a monthly expense cap. If your expenses approach the cap, notify the client in advance rather than surprising them on the invoice.

Monthly Retainer vs. Milestone Invoicing

Monthly Retainer

A retainer invoice is sent on the first (or last) business day of each month. It covers a pre-agreed scope — typically X hours of consulting per month. If the client uses more hours, you invoice separately for the overage at your standard rate. The retainer invoice is simple:

Monthly Consulting Retainer — March 2026
Includes: up to 10 hours strategic advisory
$2,500.00 + HST $325.00 = $2,825.00 — Due April 1, 2026

Milestone Billing

For a fixed-fee project, break payments into milestones tied to deliverables:

• Milestone 1 — Project kickoff & discovery (30%): $3,000
• Milestone 2 — Draft strategy document (40%): $4,000
• Milestone 3 — Final delivery & presentation (30%): $3,000

Invoice for each milestone when it is completed and approved, not in advance. This protects both parties.

Late Payment Clauses

Corporate accounts payable departments are notorious for paying late. Protect yourself by including explicit late payment language on every invoice:

"Payment is due within 30 days of the invoice date. Accounts unpaid after 30 days are subject to a late payment charge of 1.5% per month (18% per annum) on the outstanding balance."

In most Canadian provinces, you are legally entitled to charge interest on overdue commercial invoices — but only if it is stated in your contract or on your invoice. Adding this language costs nothing and significantly improves payment behaviour.

Related Templates and Guides

• Retainer Invoice Template — monthly recurring billing structure
• Project-Based Invoice Template — fixed-fee milestone billing
• Hourly Rate Invoice Template — time and materials billing
• Ontario Invoice Template — HST 13% invoicing for Ontario-based consultants
• Canadian Freelance Invoice Template
• Not sure whether free or paid invoice software is right for you? Our guide breaks it down.