What is A2P 10DLC?
Application-to-person messaging over 10-digit long codes
Short answer
A2P 10DLC is the US carriers' registration system for business texting from ordinary 10-digit numbers. Unregistered traffic is filtered or blocked.
What it is
When a company, rather than a person, sends texts from a standard local number, carriers treat it as application-to-person traffic and require registration: the brand (the legal business), each campaign (what the messages are for, with samples and the opt-in method), and the numbers used. Registered campaigns get higher throughput and fewer blocked messages; unregistered ones are increasingly dropped.
A tax firm texting through a platform is usually registered under the platform's or its own brand, with a campaign type such as "customer care" or "account notifications" and opt-in language that matches its intake form.
Why it matters for a tax firm
If reminders are not arriving, 10DLC filtering is a likely cause. Registration also forces the firm to write down how clients opt in and what the messages say, which is the same homework the TCPA requires.
Related terms
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Sources
Questions about A2P 10DLC
Does 10DLC apply to texts sent from my own cell phone?
No. It applies to traffic sent by software through a messaging provider. A person texting from a handset is person-to-person traffic.
Why are my clients not receiving our texts?
Common causes are an unregistered or mismatched 10DLC campaign, messages that look like marketing without opt-in on file, or links that carriers flag. Check registration with your provider first.
Last reviewed: October 16, 2026. This glossary explains terms; it is not legal or tax advice. Check the cited source for the current rule.
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