Which is the correct phrase? You should use 'to whom' or 'for whom,' and avoid:

The correct phrase involves understanding the proper usage of "to whom" and "for whom." In standard English grammar, "whom" is used as the object of a preposition or verb, while "who" is used as the subject.

When the preposition is "to," it should be followed by "whom" since it refers to the person receiving something or being addressed. Similarly, "for" precedes "whom" when indicating the person that something is intended for or related to. Therefore, both "to whom" and "for whom" are grammatically correct phrases to use in formal writing.

On the other hand, using "to who" or "for who" is not standard and is considered incorrect in formal contexts. Such phrases confuse the subject and object forms of the pronoun. Hence, the appropriate guidance is to avoid "to who" and "for who," making the use of "to whom" and "for whom" necessary and correct. This understanding reinforces the importance of selecting the right pronoun based on its grammatical role in a sentence.