There might be a case when you apply to a job and are required to include salary requirements in a cover letter of your resume.

First of all, it is recommended to avoid indicating the salary expectations in cover letters unless explicitly been asked for. This is because you will not have an idea about the job desription and salary ranges until you will receive the job offer and/or the interviewer will raise this issue. This would lead to premature and ineffective decision at the preliminary stages.
Therefore, remember to include your salary requirements (i.e. salary expectations) only when you have been asked for this piece of information.

So how would you do that?
This article deals with the elements that comprise the salary range for a job opening. The article also discusses on the way one should include the salary requirements in his cover letter and provides a sample letter for the same.

How to write salary requirements in a cover letter?

The dilemma starts with the fact that most (if not all) job hiring ads do not contain the employer salary limits.

The employer position:
The employers require this info to have an understanding of your salary expectations for having their first selection criteria. In fact, it appears that you find yourself with 3 no-win situations:

1. If they find that you are looking for a higher salary, they will not waste any further time since they will not be able to pay you that amount.

2. They might have the idea that you will not be happy working for a lower salary.

3. On the other hand, if your current expectations are lesser, you would land yourself with a lower salary package.

That is why your salary requirements in the cover letter have to demonstrate your desire to keep the door open.

Your position:

1. You can state that your salary package is negotiable based on the overall compensation offered including the benefits.

2. You may provide a base amount salary (from-to) after research the current market like $50,000 – $75,000 - where the lower number is your original salary expectation.
Both these options put you in a good position since they offer you flexibility during the salary negotiation stage.  

Salary expectations and salary requirements cover letter

Before writing the cover letter that includes your salary requirement, you have to research the avarage salaries of the position based on several variants. Make sure you take a good look at the following factors:

Salary survey and salary range
You need to spend time reading the current industry reviews (salary surveys) and the salary ranges for people having a similar career status to the one you are applying to.

The company field
It is also necessary to look into the field of the hiring company as their salaries mostly depend on the industry they are engaged in.  

Job location
Cost of living also forms an important part in determining your salary since they differ from location to location. For example – a financial advisor in New York is paid higher than one from Arizona as these two places have cost of living gap. The job location hence needs to be kept in mind during your research.  

Demand Vs Supply
This is one of the most important factors for determining the salary range. If the industry is crowded with a lot of people with the same qualifications and skill set, the employers gain the upper hand resulting in a lower salary being offered than would have been the case when people were in short supply for the required position.
In the other hand, if the demand and the supply are high, like in the case of s/w programmers, the company would want to grab these employers from the market and therefore offers a high salary package in order to be the first company to hire these employees.  

Compensations including benefits
Some professions (like marketing and sales) are based on benefits. You need to find out not only the salary range but also the total compensation structure that comprises all benefits for a given position – this is called the total Cost to Company or simply CTC.

Comparing apples to apples
Some professions require more competencies then others. The hiring company is going to take your overall skills, experience and qualification as their factors of the pay. Therefore, these points should be bold at your cover letter or at your resume.

Sample cover letter with salary requirements

Refer to the article – resume cover letter samples  
Fisrt draft:
As regards to your request, I have researched the market based on the job description and have come out with a salary range of $50,000 – $70,000 without any benefits or supplements added to the scale.
This is negotiable depending on the total compensation, career growth opportunities and other factors.

Thank you for your time reading this letter.
Sincerely,

Second draft:
As for the salary requirements, my expectations are as follows – $X.
However, I trust you consider this figure following a job interview as I am flexible to negotiate the total job offer aspects.