Merchants will reverse the commission it pays MyPoints requiring us to reverse the Points associated with that transaction if you return an item or items from your purchase, cancel your order, exchange an item in-store, or if the merchant determines MyPoints should not be credited with the sale. Merchants often take credit for a purchase if their coupons or discounts are applied in which case the credit to MyPoints would be reversed. This policy is covered in our Terms of Service
"MyPoints reserves the right to adjust your Point balance with award reversals for items returned or transactions not completed or cancelled. A pattern of placing orders followed by cancellations is construed as purchasing fraud and could result in the termination of your MyPoints account."
If your transaction was a return/exchange, please note that if the exchange order was not placed via MyPoints or occurred in store, MyPoints will most likely not be credited for the transaction by the merchant and thus your Point reversal will stand.