Search from various English teachers...
Calla Lily
I'm writing to you or I'm writing you?

Hello there, 
When I write a letter to someone at beginning of paragraph.

Should I use A or B, which expression is the formal sentence?

A I am writing you about your letter
B I am writing to you about your letter

Thank you,

Dec 10, 2016 12:12 PM
Comments · 3
3

In British English, 'to' would never be omitted in that sentence. Only sentence B is correct in BrE.

In American English, both are correct. Whether one is more formal I don't know, although I'd guess the omission of 'to' would make it less formal.

December 10, 2016
1
Paul is correct about these sentences in American English.  His guess is also correct. :)
December 11, 2016
I am writing to you about the letter you sent me last week.  
I wrote a letter to James that he might come to my house next week to in order to finalize the settlement. 
December 11, 2016
Calla Lily
Language Skills
Chinese (Mandarin), Chinese (Taiwanese), English
Learning Language
English
Articles You May Also Like
Same Word, Different Meaning: American, British, and South African English
12 likes · 8 Comments
How to Sound Confident in English (Even When You’re Nervous)
13 likes · 11 Comments
Marketing Vocabulary and Phrases for Business English Learners
10 likes · 4 Comments
More articles