How is the $100,000 marketplace facilitator threshold calculated?

To calculate whether a marketplace facilitator meets the sales threshold, the facilitator should combine its own sales and sales it facilitated for marketplace sellers on its marketplace occurring during the previous 12-month period. If the combination of those sales exceeds $100,000, the marketplace facilitator meets the threshold.  For purposes of applying the $100,000 threshold, marketplace facilitator should include all retail sales, including exempt retail sales, but should exclude sales for resale.