I have the Amex Aspire and track all my points earnings carefully. IME the HH points awarded from the CC for a given month factors in any refunds to the CC account during that month's billing cycle. Amex also factors in the points multipliers (e.g. Aspire earns 7 points per dollar at restaurants, 14 points per dollar at HH properties, etc.) for each specific credit to your account. As an example, I had a credit from an HH property in my last billing cycle and Amex deducted 14 points per dollar of the credited amount from the total HH points awarded for the month.

I've also had credits from charges made during prior billing cycles and the HH points deduction behavior was the same, including the various multipliers. I've never had a case where the amount of credits in a billing cycle would result in a negative net HH points awarded however, so I can't offer any experience on that.

I realize that the Amex Biz card is a different card from the Aspire, but I suspect that the HH points behavior would be identical.