Commas for Special Emphasis

This is determined solely by the writer. If a Writing.lifetips.com/cat/56416/commas/index.html">comma is used before the phrase, it must also be used after the phrase and vice versa (unless the sentence naturally requires one of the commas.)

Ex: We require a letter from your bank, on bank letterhead, stating that you are an authorized signer.

or

Ex: We require a letter from your bank on bank letterhead stating that you are an authorized signer.