Glossary
What is Transactional SMS?
A transactional SMS is a text about something a person has already arranged or asked for, such as a booking confirmation, a reminder or a delivery update.
The ICO calls these service messages. Its guidance says a message sent purely for administrative or customer service reasons isn't direct marketing as long as it doesn't promote anything, so the PECR consent rules for marketing don't apply. Add even a small promotion and the ICO treats the whole message as marketing, even if the promotion wasn't the main point.
'Hi Priya, your table for 4 at 7:30pm on Friday is confirmed' from a Leicester restaurant is a service text. Tack 'and 20% off desserts this month' on the end and it isn't any more.
You decide which kind of text you're sending, and CaptiFi Connect follows your lead. On the Send SMS page the opt-out line is off unless you switch it on, the API adds it only when you set append_opt_out, and campaigns add it unless you turn it off.