Commissions are a form of variable-pay remuneration for services rendered or products sold. Commissions are a common way to motivate and reward salespeople. Commissions can also be designed to encourage specific sales behaviors. For example, commissions may be reduced when granting large discounts. Or commissions may be increased when selling certain products the organization wants to promote. Commissions are usually implemented within the framework on a sales incentive program, which can include one or multiple commission plans (each typically based on a combination of territory, position, or products).

Payments are often calculated using a percentage of revenue, a way for firms to solve the principal–agent problem by attempting to realign employees' interests with those of the firm. However, models other than percentages are possible, such as profit-based approaches, or bonus-based approaches. Commissions allow sales personnel to be paid (in part or entirely) based on products or services sold, rather than just hourly or based on attempted sales. Although many types of commission systems exist, a common methodology to manage total spend is known as on-target earnings. On-target earnings represent a salesperson's base pay, plus expected commissions (assuming the salesperson meets a quota). On-target earnings help salespersons estimate their expected total compensation, should they meet company-specified goals.

One of the most common means of attempting to align principal and agent interests is to design incentives tracking agent performance. There is a high degree of variability in terms of types of compensation plans, such as fixed salary, straight commissions, or a combination of both. Often, commissions are awarded for reaching a sales goal called a quota. Also, commission structures can include multiple levels of attainments, each with a different threshold and associated rewards.

A commission structure can apply to employees or independent contractors. Industries where commissions are common include car sales, property sales, insurance booking, and most sales jobs. In the United States, a real estate broker who successfully sells a property might collect a commission of 6% of the sale price.

In a case from the 19th century that is still referred to today, Murray v. Beard, 7 N.E. 553, 554-55 (N.Y. 1886), the New York Court of Appeals held that under New York's faithless servant doctrine a disloyal broker could not recover commissions from his employer, holding that "An agent is held to uberrima fides in his dealings with his principal; and if he acts adversely to his employer in any part of the transaction ... it amounts to such a fraud upon the principal, as to forfeit any right to compensation for services."

In 2011, California Governor Jerry Brown signed into law AB 1396 amending the California Labor Code requiring all employers who pay commissions to enter into written contracts with their employees regarding how commissions will be earned, computed and paid. The new law, effective on January 1, 2013, further states that commission excludes "short-term productivity bonuses such as those paid to retail clerks" and "bonus and profit-sharing plans, unless there has been an offer by the employer to pay a fixed percentage of sales or profits as compensation for work to be performed".

Trail commission (TC) is commission paid by investment management companies to financial advisers. It is generally around 0.1% to 0.9% p.a. of the value invested by a client.

If an investment is made directly through a financial adviser, TC is generally kept by the adviser.