Ontario’s Construction Act gives you the right to be paid within 28 days. But that clock only starts when you send a proper invoice. Send an invoice that’s missing even one of the required fields and the owner can issue a deficiency notice, the clock never starts, and you’re back to square one.
Most trade contractors in Ontario don’t know this rule exists. They use a Word template or a QuickBooks default, send it off, and then wonder why payment is still outstanding six weeks later. The reason is usually a missing field: no period of work, no contract reference, or an HST number buried in the footer without the tax amount stated separately.
This article breaks down exactly what section 6.1 of the Ontario Construction Act requires, shows a compliant sample invoice, and gives you a six-field pre-send checklist. For broader context on how the full 28-day system works, including the payment chain, dispute windows, and what to do if a customer does not pay, see the Ontario Construction Act prompt payment guide or the 2026 Construction Act amendments guide.
Why “proper” matters: the 28-day clock won’t start without it
The prompt-payment regime under the Construction Act is powerful, but it is conditional. Section 6.4 says the owner must pay within 28 days of receiving a proper invoice. Not just any invoice: a properinvoice. If your invoice does not meet the definition in section 6.1, the 28-day obligation never attaches.
Before January 1, 2026, an owner had 14 days to issue a deficiency notice pointing out missing fields. That window was cut to 7 days by the 2026 amendments (confirmed in O. Reg. 306/18). So the feedback loop is faster now. But missing a field still resets the clock to zero once a deficiency notice arrives.
Note the distinction between two separate notices:
- Deficiency notice (7 days): issued when the invoice is missing required fields. The clock never started in the first place.
- Notice of Non-Payment (14 days): issued when the invoice is a proper invoice but the owner disputes the amount. The clock did start; the owner is disputing the sum.
A deficiency notice is far more damaging to your cash flow because it means you have to reissue and start over. Get the fields right the first time.
The 6 mandatory fields under section 6.1
Section 6.1(1) of the Construction Act lists the elements that a proper invoice must contain. Here is each one, translated from statutory language into plain contractor terms.
1. Date of invoice
The invoice must include the date it was issued. This sounds obvious, but many contractors use the work date rather than the invoice date, or leave the field blank in a template. The invoice date is what triggers the 28-day clock. Use a specific calendar date, not a vague reference like “upon completion.”
Example: “Invoice date: May 8, 2026”
2. Contract reference
The invoice must describe the services or materials supplied in enough detail to identify the contract. In practice, a job address combined with a contract date is the safest approach. A purchase order number also works if one was issued. Vague descriptions like “labour and materials” with no site reference will not satisfy this requirement.
Example: “Per contract dated April 3, 2026, for panel upgrade at 412 Lakeshore Rd., Burlington, ON”
3. Period of work
This is the single most commonly missing field. The invoice must state the period during which the services or materials were supplied. A specific date range is the clearest way to satisfy this. This field also matters for lien purposes: your lien rights depend on the last day you supplied services, and the invoice is the primary record.
Example: “Work performed: April 7–18, 2026”
4. Amount claimed and basis
The invoice must state the amount being claimed and the basis for the calculation. “Amount: $4,200” on its own is not enough. You need to show how you got there: hours times rate, materials at cost, or a reference to a schedule of values in the contract. A line-item breakdown is the clearest format and the hardest to dispute.
Example: “Labour: 24 hrs @ $120/hr = $2,880. Materials (see attached schedule): $1,320. Subtotal: $4,200.”
5. HST/GST registration number and tax amount
The invoice must include your HST or GST registration number and must state the tax amount separately from the base amount. Combining them into a single “total including HST” line does not satisfy the requirement. The CRA also requires this separation for input tax credit purposes, so this field protects both you and your client.
Example:“HST (BN 123456789 RT0001): $546.00. Total: $4,746.00.”
6. Payment remittance contact
The invoice must include the name, title, mailing address, and telephone number of the person or office to whom payment is to be sent. This is the field most contractors miss. Putting your business address at the top of the letterhead isn’t enough on its own. The remittance contact is treated as a separate, explicitly required item.
Example: “Remit payment to: Jamie Kowalski, Owner, Kowalski Electric Inc., 12 Workshop Lane, Toronto ON M4M 1A1, (416) 555-0142, accounts@kowalskielectric.ca.”
Many contractors also add a typed “Authorized by:” line for clarity. That’s good practice, but it doesn’t replace the remittance contact.
The “seventh field”: what owners can reasonably demand
Section 6.1(6.1), added by the 2026 amendments, allows owners to require additional information that is necessary for the proper functioning of their accounts payable system, as long as the request is reasonable. This means an owner can ask for a purchase order number, a cost-code breakdown, or a specific invoice format, provided they notify you in advance.
Two things owners cannot require: they cannot make a proper invoice conditional on the owner’s approval, and they cannot make it conditional on payment certification. Those requirements would let owners delay the clock indefinitely, which is exactly what the Act was designed to prevent.
Practical advice: ask at contract signing whether the owner has an AP system with specific requirements. Get the list in writing. Add those fields to your template for that project so every invoice is compliant from day one.
Sample compliant invoice
The table below shows what a compliant proper invoice looks like for a typical trades contractor in Ontario. All six mandatory fields are present.
| Field | Sample value |
|---|---|
| Contractor name and address | Kowalski Electric Inc., 88 Dundas St. W, Oakville, ON L6M 3J9 |
| Invoice date (Field 1) | May 8, 2026 |
| Contract reference (Field 2) | Per contract dated April 3, 2026, panel upgrade at 412 Lakeshore Rd., Burlington, ON |
| Period of work (Field 3) | April 7, 2026 to April 18, 2026 |
| Amount and basis (Field 4) | Labour: 24 hrs @ $120/hr = $2,880 | Materials (attached schedule): $1,320 | Subtotal: $4,200 |
| HST registration + tax (Field 5) | HST BN 123456789 RT0001: $546.00 | Total: $4,746.00 |
| Payment remittance contact (Field 6) | Remit to: Jamie Kowalski, Owner, Kowalski Electric Inc., 12 Workshop Lane, Toronto ON M4M 1A1, (416) 555-0142, accounts@kowalskielectric.ca |
The remittance contact (name, title, mailing address, telephone) IS one of the six mandatory section 6.1 fields, even though it’s the most overlooked. Including it removes any excuse for a misrouted payment.
The 7-day deficiency notice rule
As of January 1, 2026, an owner has exactly 7 days from receiving your invoice to issue a deficiency notice if they believe it is not a proper invoice. If they miss that window, the invoice is deemed to be a proper invoice regardless of any missing fields, and the 28-day payment clock runs from the date they received it.
Before 2026 that window was 14 days. The cut helped contractors. Owners and GCs used to use the full 14-day window as a de facto extension: issue a technical deficiency notice on day 13, reset the clock, buy another 28 days. That tactic is harder to pull off now because the window closes faster.
What the deficiency notice must contain (as tightened by the 2026 amendments):
- The specific field or fields that are deficient (a generic “invoice is incomplete” will not satisfy the requirement).
- What the contractor must do to address the deficiency.
- Any amounts the owner intends to withhold pending correction.
A vague or over-broad deficiency notice can itself be invalid. If you receive one, read it carefully. If it does not identify a specific missing field, consider responding in writing that the notice does not satisfy the Act and that the 28-day clock is running. Keep records of every send date and every response.
This is separate from the Notice of Non-Payment process. A Notice of Non-Payment (Form 1.1) is used when the invoice is a proper invoice but the owner disputes the amount or quality of work. That notice must arrive within 14 days of the proper invoice and must itself be specific about the disputed amount and reason. For more on the adjudication path after a dispute, see our article on ODACC adjudication in Ontario.
Pre-send checklist
Run through this before you send any invoice for construction work in Ontario. It takes 60 seconds and it is the difference between a 28-day payment and a 90-day collections headache.
If every row passes, send the invoice and note the date. Your 28-day clock starts on receipt. Set a reminder for day 7 (deficiency notice window closes), day 21 (one week out, send a courteous follow-up), and day 28 (payment due). Also check your lien deadline separately: it runs from the last day you supplied services, not from the invoice date, and missing it means you permanently lose your most powerful collection tool.
This article is for general information only and does not constitute legal advice. For advice specific to your situation, consult a construction lawyer licensed in Ontario.