If you notice a difference in Total Sales when comparing Polar to Shopify, make sure you're looking at Total Sales in the Sales Report on Shopify Analytics, not the Shopify Homepage. On the Shopify homepage, the returns also include tax and shipping of the returned orders for that day; alternatively, Shopify Analytics does not include tax and shipping. When comparing to Shopify Analytics data to Polar, make sure you select the filter "Sale Kind = 'order'" on Shopify.