I want to say "I will let you know when I have more information" in Spanish. I want it to be formal. Would this be correct:

Le avisaré cuando tenga más información.

absolutamente. To make it even clearer you might add "yo" after "cuando."

Another point is "información" usually refers to only one piece of information, so you could use "informes" which would be pieces of information.

Sra

surrrrrrrrrreeeeeeeeeeee.........................................................?

Yes, your translation is correct for saying "I will let you know when I have more information" in a formal way in Spanish. Here's how you arrived at the translation:

To say "I will" in Spanish, you use the first person singular future tense of the verb "to let someone know" which is "avisar." So, "I will let you know" can be translated as "Le avisaré" in Spanish.

To express "when" in Spanish, you use the word "cuando."

To say "I have" in Spanish, you use the first person singular present tense of the verb "to have" which is "tener." So, "I have more information" can be translated as "tenga más información" in Spanish.

To make the phrase formal, you address someone as "usted" and use the formal second person possessive pronoun "su." However, since the possessive pronoun is not used in this sentence, all you need is to use "usted" as the indirect object pronoun, so "Le avisaré" is correct for a formal context.

Putting it all together, "I will let you know when I have more information" in a formal way can be translated as "Le avisaré cuando tenga más información" in Spanish.