Net sale is what the customer paid after refunds, less sales tax, including the shipping they paid. Cost is the supplier's price-list cost plus freight, replaced by the supplier's invoice total when it arrives; freight is estimated from the supplier's freight table until then. Card fees are 2.9% + $0.30 per charge, from the Shopify Payments payouts; refunds don't return them. Contribution is net sale less cost and fees. An order without a cost counts at the costed orders' gross margin until it has one. Commissions are paid on each order a rep closed: 10% of its gross profit at a 24%+ margin, 8% at 18–24%, nothing under 18%. Website orders earn none. Fixed costs are people, software and rent for the month, entered from the month's bills. The floor is an 18% gross margin: sale minus supplier cost and freight, before card fees. Reps may discount to the 22% Target on their own; below it needs your OK.

When you drop-ship, customers pay before you pay the supplier. That money sits in your account for days or weeks, but it isn't yours: it's already spent on the order. The same goes for sales tax until the return is filed.