How to Write the Subject Line of a Business Letter

In your professional life, you need to write business letters in many situations for different purposes. Whether you apply for a job or terminate someone from his or her position, the professional world’s usual practice is to communicate through writing a letter.

If you study the structure of a letter, you will find different important parts in it. You may find some of the parts confusing or may want to know more about them. I have been teaching business writing for a couple of years, and I find many of my students utterly confused about a letter’s subject line.

The questions that I frequently experience are, “Is it mandatory to write a subject line? Why do I need a subject line? Do I need to write a complete sentence as a subject line? Where should I put the subject line? Which format should I follow—British or American?” and the like.  

If you also have such questions, no worries. In this post, I will discuss the ins and outs of a business letter’s subject line.

The subject line of a letter must be short, specific, and placed between Salutation and the Body of the letter. You can write a subject line in uppercase or boldface, and if the emphasis is required, it can be aligned center. The subject line of a letter helps the recipient understand what the letter is about.

Later in this article, I will also briefly discuss the different types of business letters as well as their purpose.  

What Is a Subject Line of a Business Letter

The subject line of a letter indicates the letter’s purpose in a very short and simple way. By reading the subject line of a letter, the receiver can understand what the letter is about. She or he does not even need to read the whole letter. When you write a business letter, you must consider that your reader does not have that much time, and she or he will just skim the letter.

Sometimes, only skimming the letter may become difficult to have a clear idea about the letter’s purpose. A subject line can make this job easy. Just reading the subject line (a few words; not even a complete sentence), one can clearly understand what the issue is that the letter refers to.

[Sender’s Address


[Inside Address


[Subject Line


[Complementary Close

[Signature & the Printed Name of the Sender

Sample Business Letter Format

Do You Really Need a Subject Line in a Business Letter?

Many business professionals think that the subject line is not essential. Yes, it is not mandatory, but using a subject line may greatly help to have easy and sound communication through a business letter. Though many out there consider a subject line as an optional part of a business letter, I would like to recommend writing a subject line in a business letter.   

Suppose the letter is too short, and the receiver can immediately understand reading it. In that case, you may not need a subject line. But if you still want to put a subject line, it is good. However, if the letter is comparatively long and has details of any issue, you should add a subject line. It will help your receiver to understand the purpose of the letter in a short time.

Where to Put the Subject Line in A Business Letter

As a letter has different parts, you may get confused about which part you should put at the beginning, which is in the middle or end. You can have a look at Sample Business Letter provided in the above part of the post.

The ideal place to put a subject line is between the Salutation and the Main Body. You can also put the subject line between Inside/Receiver’s Address and the Salutation. However, you can keep a blank line before and after the subject line to increase readability.

Dear Mr. Jason, [Salutation]

Subject: Invoice no. 3522 [Subject Line]

With reference to the above invoice… [Body]  
Sample 1: Placement of a Subject Line

Subject: Invoice no. 3522 [Subject Line]

Dear Mr. Jason, [Salutation]

With reference to the above invoice… [Body]  
Sample 2: Placement of a Subject Line

How Should a Subject Line Be in A Business Letter

There are some common methods of writing a subject line of a business letter.

  • Write “Subject:” and then mention your subject of the letter.
  • Use “Re:” instead of “Subject:” if you write to correspond with a large company. “Re” refers to “Reference” that is also used for legal correspondence. When you use “Re:” it means you are using a “Reference Line,” not a subject line. Yet, both Subject Line and Reference Line serve the same purpose.
  • Use UPPERCASE or Boldface to write the subject line.
  • Keep left-aligned or centered (in special occasions, where more emphasis is required).
  • Keep a blank line before and after the subject line.

How to write a Subject line in British and American English

Both the British and American English allow subject line in a business letter. The only difference they have is in the placement of the subject line.

In British English, the subject line is placed between the Salutation and the Body of the letter.

Subject Line in British English

In American English, the subject line is placed between the Inside/Receiver’s Address and Salutation.

Subject Line in American English

Business Letter Is an Important Type of Business Writing

Offer Letter

Letters, e-mails, memos, proposals, reports, press releases, resumes are some of the very popular types of business writing. Among them, letters are considered the most common type: cover letter, inquiry letter, complaint letter, and acknowledgment letter.

When you expect information (i.e., price, specification, availability) about a laptop of HP, you write an inquiry letter to HP. If you experience any problem using any product of Samsung, you write a complaint letter to Samsung. When you join a new company, you write a joining letter.

The table shows different common types of business letters and their purpose.

Letter TypePurpose
Acknowledgment LetterTo confirm something—confirm receiving an order, acknowledge mistakes, and informing the receiver that their previous messages have been received.
Appointment LetterTo affirm that the employee has been selected for the position she or he has applied for.
Apology LetterTo ask for forgiveness.
Complaint LetterTo complain about any product or service.
Inquiry LetterTo inquire about something.
Job Application LetterTo provide information about the qualifications, skills, and experience and apply for the vacant position.
Order LetterTo order products or services from a supplier or a seller.
Resignation LetterTo officially inform the authority that you want to quit the job.
Recommendation LetterTo recommend an employee to another company.
Sales LetterTo introduce your business to potential customers and request to take action.

In Conclusion


When you write any business letter, you must consider that your reader has limited time. You should not make your letter too long with unnecessary words. Your audience expects you to directly talk about the matter and clarify the purpose of the letter. You can have the following parts in your business letter. They must appear in the letter according to the following order.

  1. Sender’s Address
  2. Date
  3. Inside/Receiver’s Address
  4. Salutation
  5. Subject line
  6. Body
  7. Complimentary Close
  8. Signature & Printed Name of the Sender
  9. Enclosure (If Any)

If you still need any suggestions about Business Writing, you can comment below; we’ll try to give you feedback.

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Niaj A A Khan

Niaj A A Khan is an ESL Instructor with over 7 years of experience in teaching & developing resources at different universities and institutes. Mr. Khan is also a passionate writer working on his first book, "Learn English at Ease."

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