CASL and Law 25: What Quebec Contractors Need to Know Before Sending Invoice Reminders by SMS

A contractor in Laval finishes a plumbing job, sends the invoice, and hears nothing for two weeks. He wants to follow up by text. His first thought: "Am I allowed to do this?"

The answer is yes, but with a couple of important conditions. Most contractors don't know the specific rule that makes it legal, or what changes when those conditions aren't met.

This post covers what CASL and Law 25 actually say about invoice reminder texts, what you need to do when a client says stop, and why automated tools handle the compliance details you shouldn't have to track manually.

What CASL covers

CASL (Canada's Anti-Spam Legislation) applies to commercial electronic messages — emails and text messages sent for a commercial purpose. The general rule is that you need consent before sending one.

But there's an exception that covers most contractors sending invoice reminders.

Section 6(5) of CASL exempts messages sent to complete or confirm a commercial transaction that the recipient has already agreed to. An invoice reminder for work you've already done and that the client has already agreed to pay is exactly this: a message completing a commercial transaction.

The two conditions that must both be true:

First, there must be a pre-existing business relationship. You've done work for this client before. You have a contract, a signed quote, or an invoice they owe. They are not a cold contact.

Second, the message must relate directly to the transaction. A text saying "invoice #142 for $1,850 is now 14 days past due, pay here: [link]" is transactional. A text saying "while I have you, we're also running a spring promotion on furnace maintenance" is not. The moment a message adds a promotional element, the exemption no longer applies cleanly.

If both conditions are true, you do not need prior written consent to send the reminder.

If either condition is false (the person is a new prospect, or your message includes a promotional offer), standard CASL consent rules apply. For the official guidance, see the CRTC's official CASL resource.

When a client says STOP

CASL requires that every commercial electronic message include a clear unsubscribe mechanism. For SMS, the standard is replying STOP. When a client does this, you must stop sending them commercial messages promptly, within 10 business days under CASL.

There is no exception here. Even if the invoice is legitimately overdue, a client who has opted out cannot receive further SMS reminders. You can still follow up by phone or by email through a separate channel. But the SMS channel is closed.

Tracking opt-outs manually across dozens of clients is error-prone. This is one of the real compliance risks for contractors managing their own reminders.

What Law 25 says

Quebec's Law 25 (formally, the Act respecting the protection of personal information in the private sector) governs how businesses collect, use, and store personal information about their clients. It applies to any Quebec business, including sole proprietors doing trades work.

The practical implications for invoice reminders: you can store a client's phone number to send them reminders about their own invoice. That's the purpose for which you collected it. Using it to send unrelated marketing to that client without consent goes beyond the original purpose.

You should not keep client personal information longer than necessary. Once a client relationship has ended and all invoices are resolved, you don't have an indefinite right to that data.

If a client asks what information you hold about them, or asks you to delete it, Law 25 gives them that right. For most small contractors, this means having a basic process, even an informal one, for responding to those requests. The full text of the Act is available on LégisQuébec.

Law 25 does not prevent you from sending invoice reminders to your existing clients. It just requires that you handle their data with reasonable care and purpose limitation.

Quiet hours

CASL and Law 25 don't specify communication hours, but Quebec consumer protection norms mean you shouldn't be texting clients at 11 PM about an overdue invoice. The industry standard for business SMS is 8 AM to 9 PM in the recipient's time zone.

What good practice looks like

Include STOP instructions in every SMS. Even when consent isn't required, the opt-out mechanism must be present.

Keep reminders transactional. Invoice number, amount, link to pay. No upselling in the same message.

Honor opt-outs immediately. Don't send a follow-up the next day because "the system hadn't processed it yet."

Don't mix channels without a separate basis. If a client opted out of SMS, treat each channel separately and don't assume the other is still open.

For examples of messages that stay cleanly within transactional limits, see our ready-to-use reminder templates.

How Relanco handles this

Every SMS Relanco sends includes STOP instructions. Opt-outs are recorded immediately and enforced across future sends for that client. Reminders go out only between 8 AM and 9 PM Eastern. Message content is transactional by design.

You shouldn't have to track consent states and opt-outs in a spreadsheet alongside everything else you're managing. For a comparison of SMS and email as reminder channels, see our post on accounting software invoice reminders.

Frequently asked questions

Do I need consent to text my clients about overdue invoices?

Not if two conditions are met: you have a pre-existing business relationship with the client, and the message relates directly to the transaction. Under CASL s.6(5), invoice reminders to existing clients for work they've already agreed to pay are exempt from the general consent requirement.

What happens if a client replies STOP to my invoice reminder?

You must stop sending them commercial SMS messages. CASL requires you to honor opt-out requests within 10 business days. There is no exception for outstanding invoices. You can still follow up by phone or by email through a separate channel.

Does Law 25 prevent me from storing client phone numbers for invoicing purposes?

No. Law 25 allows you to store and use personal information for the purpose it was collected. If you collected a client's phone number to communicate about their project and invoice, using it to send invoice reminders is within that purpose. What Law 25 requires is that you don't use it beyond that purpose and that you don't keep it longer than necessary once the relationship ends.

Sending invoice reminders by SMS to your existing clients is legal. The rules exist, they're clear, and following them isn't complicated if your tool handles them for you.

Try Relanco free for 30 days →

Read also: 5 Invoice Reminder Email & SMS Templates That Get Contractors Paid Faster