This is disappointing but it does happen. Companies do not pay out commission on returned goods. You need to be aware of this to avoid fall into further pitfalls. No one would expect to be paid a commission on a returned item however; some less than honest affiliate marketing companies can use this to scam some of your profits. You need to make sure you understand their return policy and how it will affect the amount that you are paid.
A return occurs of course when a customer brings an item back. Charge backs can also happen when they dispute an amount on a credit card. Be sure you keep a close watch on which items are being chargeback or returned. See if there are any patterns that are obvious. If you notice that the orders that are charged back are always very high ticket orders then they could be giving you false information. They are doing this to keep you commission down and keep some for themselves. Keep a close eye on returns especially if you think it is happening a little too often.
Charge backs are also indicative of another more serious problem. If you notice that many of these charge backs are happening during an initial trial period, or the money back guarantee time, then there could be further problems. This is a sign that the product or service that you are promoting isn't up to customer satisfaction. It could be misleading or just poor quality. However, it will effect your commission and your future as an affiliate marketer. If this seems like it is happening a little too often then again, there are problems somewhere in the company. Look to get out and make alternative arrangements.
You also need to be aware of which items are actually commissionable. Make sure you understand which products you will be earning money from to avoid disappointment later. Sometimes the company will offer a selection of products to put on your site, however only certain items may be commissionable. Before agreeing to anything like this checks your terms and conditions carefully.
Finally, you also need to make sure that items that are sold don't have any other conditions attached. Some will only pay a commission if the customer fills in the payment details immediately. If they select an item and continue to shop, you may not receive any commission on that item. You can also loose commission if the customer clicks on any other links before completing the order. If they order 30 of an item you promoting but click on something else then you have lost out on quite a large amount of commission.
Affiliate marketing is a great way to earn money. However, before jumping in head first you need to read your terms and conditions carefully. It may be worth having an attorney look them over for you. You need to be aware of the many pitfall people fall into when they go into affiliate marketing. Read and understand your terms to avoid disappointment later.