Font Size: The traditional font size for a professional letter is 12. The font should be Times New Roman or Arial. However, if you are using letterhead, the letterhead may be in different font size and style. Font Style: There is no need to use different styles within a professional letter. Use a uniform font (book print font such as Times New Roman or Arial) and avoid underlining, italicizing, or bolding. However, if you are using letterhead, the letterhead may be in a different font style.
In most cases, the business letter will be the first impression that you make on someone. Though business writing has become less formal over time, you should still take great care that your letter’s content is clear and that you have proofread it carefully.