There are a number of instances where you may be asked to write a letter on behalf of someone else. Lawyers, for instance, do it regularly. Other situations include writing for people who don’t have the skills to do it themselves or who are second language learners and can’t write in English. Your boss's absence from the office may be another reason for him asking you to write a letter on his behalf. Regardless of why you are writing the letter for some else, the format is consistent.

1. Determine Content

Speak with the person you are going to write the letter on behalf of. Make a list of points to cover, the person to address the letter to and any other details that need to be included. Discuss the topic of the letter until you feel that you have enough background information to write it properly.

2. Use Letterhead and Business Letter Format

Write on letterhead if possible because it lends credibility to your correspondence. If you don’t have letterhead, type the address of the person you are writing the letter for on the top of the page, leave a space and type in the date. Start with the salutation, “Dear” followed by the person’s name, title and a comma. If, for instance you are writing to a company it would read “Dear Ms. Briggs,” or “To The Presiding Judge,” if it is to the court.

Adopt the block-format for business letters. All sentences start on the left-hand side of the page; paragraphs are separated by a line space. The distance between your closing is three to four lines to allow for your signature. Type business letters rather than handwriting them.

3. Declare Authorship

Declare that you are writing on behalf of another person if it is appropriate, such as in a letter to the court. If it is a letter going out under the other person’s name you don’t have to state that she didn’t write it herself. In the case of physical injury or language problems indicate the reason: “I am writing on behalf of Jeremy Smithers as he broke both his wrists skiing.”

4. Use Effective, Easy-to-understand Language

Get to the point. Letters – whether or not on behalf of someone else – need to be short and concise. State the reason you are writing and then start a new paragraph for your supporting ideas. Remember to change paragraphs and to leave a space when you change ideas. Write in easy-to-understand language. Don’t use a large word when a small one will do and keep your sentences short. Aim for clarity rather than trying to impress your reader with your extensive vocabulary.

5. Use a Formal Voice

Keep the tone businesslike. Avoid flowery phrases and stay focused on the topic you are writing about. Don’t offer your opinion on the subject unless there is a very good reason for doing so.

6. Close Strong

Summarize the letter's contents in the concluding paragraph. Also specify the action the person you are writing the letter for wants taken. If could be the replacement of a faulty appliance or a request for a meeting. Use the closing “Sincerely” or “Sincerely yours” to stay consistent with the business tone of the letter. Phrases such as “Talk soon” or “Your friend” are not appropriate. Sign and type your name, followed by the words "on behalf of [name of person you're writing for]."

7. Review

Leave your letter for a day or so and then edit it. As well as grammar and spelling mistakes, watch for commonly confused words such as “passed and past” or “affect and effect.” Check it against your original list to make sure you didn't forget anything. Put yourself in the place of the letter's recipient. Read it aloud to yourself and assess it for tone and content. Edit accordingly. Review the letter with the person on whose behalf you wrote. Make sure you didn't overlook anything the person wanted included.