The payments library behind Kickflip is based on Square, who manages sales tax automatically. A buyer in Oregon will not pay sales tax, while a buyer in California will. Because Kickflip is only available in the US for now, it's pretty straightforward and automatic through Square. They also very securely manage compliance around credit card entry.
Selling on Kickflip, as with any other online selling, should be reported to the IRS by the seller as income.
Finally, Kickflip uses Shippo to generate USPS shipping labels, and they also provide nice out-the-door quotes that are surfaced to the user at checkout.
Great question, thanks for asking!
