Everything worth knowing, nothing that isn't.
The consent line
The dividing question is purpose. Transactional (or 'service') messages support a transaction or relationship the user already initiated — a login code, a shipping notice, a booking confirmation — and are generally permitted without separate marketing consent because the user needs them. Marketing (or 'promotional') messages advertise products, offers, or events, and require explicit opt-in and a clear, honoured opt-out under regimes such as GDPR and the region's PDPL laws (and the TCPA in the US). Misclassifying marketing as transactional is a compliance breach, not a shortcut.
- Transactional: supports a user-initiated transaction or relationship.
- Marketing: promotes products, offers, or events.
- Marketing needs explicit opt-in + a working opt-out.
- Transactional a user requested can generally be sent without marketing consent.
Timing, sender IDs, and routing
Because transactional messages are time-critical and expected, they can be sent at any hour and are often carried on higher-priority routes to minimise latency — an OTP that arrives late is useless. Marketing is frequently restricted to daytime 'permitted hours' by regulators, and many markets require it to use a distinct promotional sender ID separate from the transactional one, so subscribers can tell them apart and operators can enforce quiet hours. Keeping the two streams and sender IDs separate is both a compliance and a deliverability practice.
- Transactional: any time, latency-sensitive, higher-priority routing.
- Marketing: often limited to daytime permitted hours.
- Many markets mandate separate promotional vs transactional sender IDs.
- Separation improves both compliance and deliverability.
Getting the classification right
The most common mistake is smuggling a promotion into a transactional message — adding an offer or a 'while you're here' upsell to an order confirmation. That reclassifies the whole message as marketing, so it now requires consent and must respect quiet hours; sent without them, it can be blocked or fined. Keep transactional messages strictly informational, run marketing on an opted-in list with opt-out handling, and, where required, register and use the correct sender ID for each stream.
- Don't add offers to transactional messages — it makes them marketing.
- Keep transactional strictly informational.
- Run marketing on an opted-in list with opt-out suppression.
- Use the correct registered sender ID for each stream.
Transactional vs marketing SMS at a glance
| Transactional SMS | Marketing SMS | |
|---|---|---|
| Purpose | Information the user requested or needs | Promoting products, offers, events |
| Consent | Generally not required (service message) | Explicit opt-in required |
| Examples | OTP, order/delivery updates, reminders | Sales, newsletters, announcements |
| Send timing | Any time (time-critical) | Often daytime permitted hours only |
| Opt-out | Not applicable | Mandatory and must be honoured |
| Routing priority | Often higher-priority / low-latency | Standard |