Businesses give various privileges, gifts, discounts and free products to their customers in order to ensure customer loyalty and encourage them to shop. One of the most preferred methods is giving free products, also known as surplus goods. However, the issue of giving surplus goods is controversial for businesses. Choosing the right customer and giving the right amount of surplus goods is difficult to determine objectively. Different criteria can be considered for giving surplus goods to customers. Some of these criteria are the amount of goods sold in the previous month, the total price of the goods, the year of working together, etc. different calculations are used. However, it is not known which of these methods is a more accurate method. This study analyses which of the metrics used for surplus calculation is more important. Firstly, a pool of criteria was created from these metrics with expert opinion. Then, 5 experts with more than 10 years of experience in customer relationship management in the sector were asked to evaluate the criteria. FUCOM method, one of the multi-criteria decision making (MCDM) methods, was used for this comparison. As a result of the evaluation, it was seen that the most important criterion for customers to give surplus goods is “Average Monthly Spent Money” and this criterion is followed by “Amount of Goods Purchased Last Month” and “Years of Working with the Customer” criteria. As a result of these findings, it will be useful for businesses to consider these criteria when determining surplus goods for their customers and to use one or more of them for surplus determination strategy.