I bought TURBOTAX PREMIER 2020 WIN ESD from custco online, and just received emial about the key and download link. But I have done the tax by online, how can I return it and get refund?
Since you purchased the software from Costco you will have to contact Costco on how receive a refund for the Costco purchase.
That is your product, and according to other support cases, you have a way to refund directly.
Take a look at your following link and to be a nice support.
That link is not a Turbo Tax website and not Turbo Tax support.
Turbo Tax Refund Policy…
You can call and ask
Contact Customer Service
5am-5pm Pacific Time
Monday-Friday
https://support.turbotax.intuit.com/contact/
What is the Turbo Tax phone number
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632