[GNC] Credit Card Rewards Refund

[rsbrux]

I have a credit card which, like a few others, accrues a small 
percentage (1-2%) of the amounts spent as a rebate.  The rebate isn't 
subtracted from each charge, but accumulates in the card account as 
"Reward Points" until I cash them in.  The amount is then credited to 
the card account as a payment.  Should such payments be recorded as 
income or as a negative expense?