SMS is the highest-open channel available to a local business by a wide margin, which is exactly why the rules around it are the strictest. The consequences of getting it wrong are not a lower open rate — they are carrier filtering, blocked numbers, and TCPA exposure with statutory damages per message.

The rules are not complicated. Ignoring them is genuinely expensive.

Consent is the whole thing

You need express consent to text someone for marketing purposes. That means they affirmatively agreed to receive marketing texts at that number, and you can show when and how.

Things that are not consent:

- They gave you the number to book a job

- They are an existing customer

- The number was on a list you bought

- They texted you once about something else

- A pre-ticked box on a form

Things that are consent: a clearly labelled opt-in where the person actively agreed, with the purpose stated, recorded with a timestamp.

There is a meaningful distinction between transactional and marketing messages. Appointment confirmations, reminders, and responses to a request are transactional. Promotions, offers, and reactivation campaigns are marketing and need marketing consent.

A2P 10DLC registration is required

Business messaging over standard numbers in the US requires 10DLC registration — the carriers' framework for identifying legitimate business senders. Without it, throughput is throttled and messages are filtered, frequently silently.

That last part is what catches people. Unregistered campaigns do not fail visibly. They just do not arrive, and the business concludes SMS does not work for them.

Registration is part of setting up properly. Any partner who does not raise it before you start sending has not done this before.

What good SMS practice looks like

Identify yourself in the first message. Every time. The recipient should never have to guess who is texting.

Include opt-out instructions and honour them immediately. STOP has to work, instantly and permanently, without exception.

Respect quiet hours. Not just because of the rules — a 9pm marketing text damages the relationship even when it is technically permitted.

Keep it short and specific. SMS is not email. One point, one action.

Do not overuse it. The channel's power comes from being uncluttered. Businesses that text weekly destroy the thing that made it work.

One practical note that costs real money: non-GSM-7 characters — em dashes, curly quotes, emoji — silently convert a message to a 70-character encoding instead of 160. A single em dash can triple the cost of a campaign.

Where SMS genuinely outperforms

Instant lead response. A text within seconds of a form fill is the single highest-value use of the channel for a service business.

Missed-call text-back. Automatic and immediate. Recovers work that would otherwise be gone with no trace.

Appointment reminders and confirmations. Reduces no-shows more reliably than email.

Time-sensitive scheduling. "We have a cancellation tomorrow at 2, want it?"

Reactivation, used sparingly, to a list where you hold real consent.

The audit worth doing before you send anything

Before any campaign, work out which parts of your existing list you actually have marketing consent for. For most businesses the honest answer is that it is a smaller list than they assumed, and some of it is not usable at all.

Sending to the rest anyway is the decision that creates liability. A partner who tells you a segment is unmailable is protecting you, even though it is not what you wanted to hear.