Text messaging is among the least formal ways of communication, especially when compared to emailing and formal letter writing. You generally are allowed only a few short sentences in which to get your point across. Despite the short messaging format, there still are some etiquette cues to keep in mind when texting.
Type up a brief text message using your phone's interface. Formal text messages should be as succinct as possible.
Leave out any filler words or text messaging lingo since this is a formal text. If the recipient is unfamiliar with these phrases, they might become confused.
Make no attempt to shorten the text message by using uncommon abbreviations. In fact, you should avoid using abbreviations altogether. If you find that you do not have enough room to get your entire message across in a single text, send an email to that person instead.
Sign your name at the end of the text. You don't need to include 'Sincerely' or 'Yours Truly'. But your name should appear following the last sentence to be sure that the recipient knows who sent the message. Also, if the message is passed along, your name will be attached to it.
Read the text aloud to make sure the tone is formal, rather than flirty, childish or unprofessional. It's difficult to convey tone through text messaging but attention to this detail will help ensure yours is formal.
Send the message. If you receive no response, do not send the message again. Instead, make a phone call or send an email to follow up.