The contribution margin on a job is the excess of sales revenue over variable costs. In other words, it is the amount of money available from a particular job or product to cover the fixed costs of the business and contribute to the profit. It is calculated by subtracting the variable costs associated with a product or job from the revenue generated by that product or job. The contribution margin is important because it helps businesses determine how much they need to sell in order to cover their fixed costs and make a profit. By understanding the contribution margin, businesses can make better decisions about pricing, production, and sales strategies.